For this demo I'm using ambrosia maple. The size of the panel is 10" wide and 19" long. The breadboard ends are 2" wide and 10 1/4" long.

It's really important that the ends of the panel be square so that when you run them over the dado stack to remove material, your shoulders end up square as well. It's worth the effort to make sure of this before moving on with the rest of the project. It is possible to fix later using a shoulder plane if for some reason you are not able to get the ends square.

My breadboards are a little longer than my panel is wide so when I mark for the stopped groove, I make sure to add 1/8" on each end to compensate for the added length.

I carry those lines around to the face.

Over at the router table I insert a 1/4" spiral bit and using a piece of tape, mark the width of the bit so I can see it while cutting the stopped grooves. I use a block of wood to help mark those lines. Note: the green tape is away from the bit far enough that the breadboard end doesn't touch it. Even though the tape is thin, it's important to keep the pieces flat and square up against the fence when running them through. 

As you can see here, When I plunge down, I make sure to line up the start line with the left side of the bit since i'm pushing the piece from right to left at the router table.

And then I stop at the second line on the breadboard end.

This was after running the board through the router table. I moved the board just a little bit while trying to turn the router off which caused the bit to take a little extra off of the inside of the piece. Not a big deal, but not what I wanted to do.

If you take the time to set your fence up, you should be able to center the breadboard end on the bit. 

Now that we have a mortise to gauge the tenon thickness, I scribe a line 1" deep on the ends of the panel. This will be the full width of the tenon.

To cut the tenon I use my table saw with a 3/4" dado stack. About 1/8" of it is buried in the fence. I set the blade to a little under 1/4" and made a pass.

It was a little snug, but I was able to get it to fit. I would rather use my rabbeting block plane to get the tenon to size rather than take a chance on my table saw.

With the blade at the correct height, I make a pass, move the fence back and make another pass until I get to that 1" width.

Next I mark the tenons. Everything in red gets removed.

I carry the lines over to the top of the panel so I can see it when cutting.

Using my pull saw, I cut on the line. When I cut the two end pieces, I stop about 1/16" from the bottom of the tenon so that I don't cut in to the end of the board.

Next I turn the board on it's side and remove the waste.

Using a chisel, I remove that 1/16" waste.

Using a combination square, I check to make sure my chisel work came out OK. Luckily it did.

To remove the waste between the tenons I use my bow saw. I stayed 1/8" above the bottom of the waste when using the bow saw, so I followed that up with a chisel.

It was time to dry fit the tenon so that I can mark for the deeper mortises. It was still a little tight so I used my rabbeting block plane to take it down just a little. I still want this to be a friction fit but don't want to have to hammer it home to get the breadboard end on.

I mark for the deeper mortises and make sure to add an extra 1/8" to the left and right of the outer two mortises. This will allow the panel to move inside of the mortises during seasonal changes. I am keeping the middle mortise roughly the size of the tenon.

And since I have the router table fence setup perfectly, I route the deeper mortises the same way. I raised the bit 1/4" at a time until I reached the depth of 1".

This is what it looked like. You can see here that I made the outer mortises wider than the marks to allow for movement.

Remember how I said the panel ends should be square? Well I had an issue with this corner as you can see.

Here's a closeup of that corner.

To fix it, I made a few passes with my shoulder plane. I started the cut on the right side of the board, pulling up right where the shoulder started dipping. To keep everything square, I made a pass on the opposite face as well.

Success!

To mark for the dowels I find the center of the tenons and make a mark.

I used my 3/8" brad point bit and made a start hole before removing the breadboard end.

When drilling the hole, I used a backer piece to help prevent a blowout on the bottom of the board.

Everything came out great.

I put the breadboard ends back on to make a mark for the holes I need to drill in the tenons.

I only marked deep enough to be able to see it. I didn't want to make this indentation too deep.

Since I'm drawboring the dowels, I move that mark 1/16" back towards the shoulder of the panel. 

And next I drilled the hole using the 3/8" bit.

All 3 holes drilled.

I'm elongating the outer two holes to allow the panel to move. I simply moved the drill side to side,  across the grain, to elongate them about 1/8" both ways.

It's important to not change the width of the opening, only the length. 

I apply the glue to only the center tenon when putting this all together. I don't want to apply glue on the outer tenons because it would restrict movement, which we want to allow.

You can see the offset holes in the tenons.

Before installing the dowels, I tapered the ends of them to help them get started past the offset holes.

I applied glue to the center dowel.

And using a hammer, I tap it in.

When I installed the outer dowels, I only applied glue to the top of the dowel and then tapped it in roughly 1/8" so it didn't get in the hole of the tenon, but the breadboard hole. This will help hold the dowels in and still allow the panel to move.

As you can see, make the dowels long enough so you don't have to be exact on the positioning.

After the glue dried I remove the excess dowels with my flush trim saw.

Next I use my smoother to clean up the breadboard ends as well as the panel.

With the panel in the vise, I flush up the breadboard ends with the side of the panel with my smoother as well.

You will notice the gap on the underside of the panel where the pins have wrapped around the offset tenon. Popular Woodworking Magazine has an excellent article/video on how to fix this if you want to hide the gap: http://www.popularwoodworking.com/techniques/mushroom-your-gaps .

Thanks to reddit user Al_Capwnd_You for pointing that out to me.

You can see the gaps a little better in this photo. This is on the bottom side of the panel. The other face of the panel doesn't have any gaps.

I applied a few coats of shellac to the surface just to give the panel some color.

Thanks for checking out this how-to. Hope you picked up a few things a long the way.