For this project I used 3 ounce chromexcel horse front leather in black and brown. I cut the leather to  2 1/2" wide by 5 1/4" long for each pen case.

To begin, I mark a line on the rough side of the leather about 1/2" from the top. This line indicates where I should start putting glue.

I use ecoweld water based adhesive because it does a decent job and doesn't stink compared to contact cement. It may not hold as good as contact cement but it holds the piece fine enough until I get a chance to stitch it.

I use a q-tip to apply the glue all the way around the leather, making sure to start and stop below my 1/2" markings.

Since i'm rounding the corners I make sure to apply a little more glue to the bottom corners so that when I cut off material, it will still be glued together.

When the glue becomes tacky, I know it's ready to fold.

I pretty much just fold the piece of leather in half length wise.

It's super important to line the edges up when glueing leather together. This prevents a lot of sanding/cutting after the glue dries to get edges flushed up.

I purchased a set of these arch shaped punches and used the 1/2" punch to put rounded corners on 2 corners of the case.

This is the top right corner with the rounded corner

And the bottom right corner with the rounded corner.

Next up I use a set of wing dividers to mark a line for the stitching. I have the dividers set to 1/8".

I trace around the right side of the case (the side with the rounded corners) to mark a line for the diamond chisels.

Next up I use a 2 prong and 4 prong diamond chisel and lightly trace around the marked line to see how things line up.

When I get to the corner, I use the 2 prong chisel

As you can see here, everything looked good so Its time to pound the chisels through the leather

I use a plastic bone folder to put force down on the leather case when pulling the chisel out. You need to remember that it's only being held together so I didn't want to risk the piece coming apart.

It came out pretty good. This is the front side.

And the back side.

For the brown case I chose 0.8 mm colonial tan ritza tiger thread, and 0.8mm black ritza tiger thread for the black leather case.

To determine how much leather you will need, I traced the chisel holes with the leather and whatever that length was, times it by 4. I usually make it a little longer than that (4.5x the length) on smaller projects just to be safe since it doesn't waste that much thread, and the thread is cheap.

I use two saddle stitching needles for stitching.

This is all the thread needed for the pen case.

I begin saddle stitching. If you want an excellent book on how to saddle stitch, check this book out: http://amzn.to/2elcFMO It's a cheap book but packs a lot of great illustrations on how to saddle stitch. A recommended buy if you want to learn how!

Got the case stitched up and looking good! Time to move on to edge finishing.

I sanded the edges with 120 grit, 220 grit and then 400 grit sandpaper to smooth everything out and to remove any dried glue. This step is super important if you want clean looking edges. When I sand the edges I sand in one direction only.

To burnish the edges I like using gum tragacanth but water and beeswax/saddle soap work just as well.

I apply the gum with a q-tip

And then burnish it with a wooden burnisher.

I apply gum to the side and then the bottom of the case. It's important to only apply the gum tragacanth to one section at a time so it doesn't dry before you have a chance to burnish it.

After the gum dries, I sand the edges with 400 grit sandpaper and then repeat the same steps above with the gum tragacanth/burnishing. I will sand and burnish this way about 2-3 more times to get a nice, clean edge.