Completed sled. Zero clearance for nice clean miters

I need to add a box on the back as a blade guard, but it's functional 

This will be a zero hand tool project. Most of my work involves hand tools, but not this time. I've got some 1/2" cherry plywood that's about 22" wide. I'm going to cut it to about 26" long

I mark the cut line, then mark the offset for the saws base. 

I then put my straight edge along that line

Worm drive saws are awesome. Indexed heights for solid materials and plywood

Cut to width

This makes things easy later. I set my fence to half the width of the sled - 13" in this case. I then mark the blade location and the miter slot locations. This does not need to be exact. I just want to avoid cutting slots or putting screws in the wrong place

In this crappy picture I transfer my marks to the bottom of the board. Since this will be a miter sled I make sure to extend the blade kerf over 45 degrees.

Now for the slots, These will hold clamps like a T-Track would. I draw the tracks centered between the blade kerf and miter track on each side.  From the back fence (where the work goes up against) I measure 2 1/4" and make a mark on each line. I will drill a 1/4" hole here

From the front fence (not where the workpeice goes) I measure 2" back on each side and plan for a 1/2" hole 

Drilling time. I am using a 1/4" bit, a 1/2" bit, and a small bit for a pilot hole

I drill the pilot all the way through, then I drill halfway with the 1/2" and 1/4" bit to prevent tear out. A sacrificial backer would work as well

Speaking of fences, this will be the fence. It's a piece of 3/4" plywood 

I rip it in half to glue it up to get a ~1 1/2" thick fence

Slot time. I am using a router, a 1/2" bit and a 1/4" bit

I start with the 1/2" bit in the router, and a straight edge

I put the bit in my pre-drilled hole and align and secure my straight edge

I route a 1/2" groove about half way though. The slot needs to be deep enough to house the nut for my hold down clamp so it won't scratch my tablesaw's surface.

Without moving the straight edge guide, I take out the half inch bit and put the 1/4" bit in. I route all the way though 

Now I have a slot for the the bolt to go through. The 1/2" hole on one side allows me to insert the clamp from on top of the jig

Rails! I like to use quartersawn hardwoods. This is oak

The miter slots are about 3/4". There is no room for play here, they have to be tight. As such I like to cut the pieces proud on the bandsaw

They are a little too big - which is good. 

Instead of trimming them on the tablesaw, I use my planer. I am confident my planer does not snipe. If your's does, make your rails long so you can cut the snipe off. Or consider using a tablesaw

They fit super snug, now to make them thinner. I want them just below the surface. Back to the planer - but the other face this time

Perfect fit

Now to attach them. This is the easiest way I know how. I add a few small nuts to the bottom so the rails are a little proud, then apply glue to the top of them. Consider taping off your tablesaw top to avoid squeeze out 

I bring the fence up again to the 13" mark and drop the sled on the rails. I put my tool chest on it for weight

While that's going on I unclamp the fence and remove the squeeze out from the bottom

I run the bottom over my wife's jointer

Now I'm going to add the front fence Being careful of where the blade will travel, I drill some countersunk holes on the bottom and screw it on. This fence is not at all critical. I attach the rear fence but with only 2 screws on the far ends. This will be adjusted 

Now I adjust the rails. They swell a little with the glue. I have 120 grit sandpaper on a square block. I take even strokes and test often until the sled slides with just a little friction. Install the fences before this step. They can add a little bit of tension

Once the rails are adjusted, I cut a kerf. I do not go all the way through yet

Now I have a slot to align the fence

The kerf is the exact size of a ruler I have. I put that ruler in the kerf and use my straight edge to check the alignment

Not even close. I remove the screw on that end and tap the fence until it's square

Once square, I clamp it. Re-drill another hole. Do not use the same one. I have enough room to leave it in the miter slots on the saw and slide it off the back

This piece of scrap is square. Here you can see the clamp in use

Test cut. I then cut it again

Square!

And a perfect miter. I then add a few more screws to the rear fence and test one more time. After that I wax up the bottom, clean the squeeze out from the top of the fence, and it's done