Per your requests, here are the steps I took to make the clutch from this post. Please note that I made a very simple version, so the end product is not lined (I plan on adding lining later, but keep the contents in a large ziploc baggie for now) and is not professional quality.
Supplies:
– Material for the clutch (leather, faux leather, cotton, canvas, etc). Determine what size clutch you want and add approximately 0.5″ to each side for the seam allowance. You will need either two pieces of material that size, or one long piece. If you want a foldover style clutch, make sure add extra length to the height for folding down. In this tutorial, I am using a 12″ x 20″ piece of material which yielded an 11″ x 7″ clutch when folded.
A note on materials – I ordered the cheetah print hair on leather from here (requested a custom size). It was listed as 1.3 mm thick, however my measurements indicated at least 2 mm thick, which I feel is too much for a standard machine needle to handle. For my red clutch shown here, I ordered “ostritch” embossed leather from the same store. That material was accurately listed at 1.2 mm thick, and was fairly easy to work with using my machine.
– A sturdy zipper. Try to find one that is the same width of your material. I got a 12″ metal zipper also via eBay.
I decided to do a “fully exposed” zipper and attach it to the outer of the material, because the leather was too stiff to bend using the proper method. Of course you can add a strip of thinner material to connect the two like many professional clutches, but I decided that this shortcut didn’t look half bad.
Step 1. Pin one edge of the zipper to the outer of your clutch material. From the backside, make sure the leather edge won’t interfere with the zipper pull. You can test the zipper after you finish pinning along where the stitches will be. 
2. Stitch along the pinned line. Make sure to back-stitch at the beginning and the end to secure the stitches. Don’t forget to remove the pins as your needle approaches!
As this leather was 2mm thick and I only had a standard duty needle, I hand-turned the sewing machine wheel to not risk breaking my needle. I believe you can do this with the machine turned off. I am a very bad hand-sewer, so I opted for this method to get evenly-spaced stitches (as shown in the photo, I had to switch my “foot” because the standard one interfered with the metal zipper). If you are sewing by hand, maybe use a thimble to assist with getting the needle through thicker materials.
Repeat steps 1 and 2 for the other half of the zipper. 
3. Turn the material inside-out and mark lines for the side seams. Stitch along the marked lines, and back-stitch once or twice at the edges for durability. If you started with two pieces of material instead of one long one, you’ll need to stitch together the bottom as well. 
Closeup – stitch the side seams all the way to the edge of the zipper, making sure not to hit any metal parts and break your needle. I opened up the zipper a little bit before “sealing” the last of the three edges.
4. Snip the bottom corners (may not be necessary for thin materials or fabrics). Get fairly close to your stitched line without cutting any of the stitches. For corners on thicker/stiffer materials, this helps keep the corner sharp after it is turned rightside-out. 
5. Open up the zipper and turn the entire bag rightside-out. For stiffer materials, press firmly down on the edges to flatten them, and use a small, sharp tool (ie. pen, pointy chopstick) to help poke out the corners. For fabric, use an iron.
All done! After making this, I found a very thorough tutorial for a DIY fabric clutch/pouch with lining (just skip the felt padding if you’re using thicker materials) and zipper here. I suggest practicing first using fabric, canvas, or another thinner material before moving on to leather.
