Step 1: Tools:

Ruler
Pencil or pen
Scalpel
Hammer
Jeweler's anvil/ vice/ metal strike plate
Tubular rivet peening tool
Rotary hole punch
2 prong lacing needle
Rubber gloves
Rags
Garbage bag or plastic sheeting
Line 20 & 24 snap setter with anvil
Fabric measuring tape

Step 2: Materials:

Black flat leather lace
6 - 7 oz. tooling sides
Coal black leather dye
(2) brass sandal buckles
7/16" tubular rivets
1/2" x 48" black leather strips
Watch head
(2) line 20 snaps

Step 3: Measuring the Leather Blank

Measure the circumference around the wearer's wrist; you'll need at least 1/2 inch or more of overlap to accommodate the snaps.
I used an 8 3/4" x 1 1/2" blank for a 8" circumference.
Cut along the measurements made with a scalpel or utility knife (make sure you have a cutting board or hard surface underneath to keep from ruining your carpet or work area).
Measure 1/8" in from the side edges. I used 15 evenly spaced holes for the edges. [I.e. Take 8" divided by 16 (you'll want one number higher than the amount of holes you intend to add) to get 0.5" intervals]. Punch all the lacing holes for the lacing and the button snaps.
Dye your leather blank (make sure to protect your work surface with plastic).

Step 4: Stitching the Lace:

Starting from the underside edge, send a good length of leather lace through, leaving, at least, 1" of tail. Make a whipstitch along the edge, leaving the first few loops raised. Place the remaining tail through these loops and tighten. Continue all the way through the last hole, then bring it back, the same way, to create a double loop.
When you get back to where you started, cross the lace over, underneath, and do the same process all along the opposite edge. When you're back at the beginning, leave some loops, send the tail through, tighten, and cut off the excess lace.

Step 5: Setting the Snaps

For this you'll need:
A hammer
An anvil
20 & 24 snap setting tool and anvil

Place the snaps in their respective arrangements and pound them into place with the setter tools (make sure to use the proper-sized setting tools, or it could ruin the snap).

Step 6: Adding the Watchband

Cut a small hole, about 1" in from the ends, large enough to accommodate the straps.
Measure one strap to span from slot to slot (this should have at least 1/2" of overlap to pin underneath).
You'll need 2 straps to hold the watch head (I used 2 at 8 3/4"). Trim the ends and add the buckle pin holes to these 2 straps.
Place the Un-trimmed end of one strap into the slot on one side; do the same for the other strap on the opposite end.
Punch a small hole through the watch strap, the runner strap, the leather blank, and (underneath) the runner strap tail and watch strap tail. Rivet these together. Do the same thing on the other side.

Step 7: Adding the Buckles

Make a hole near the base of the watchband strap for the buckle pin to go through. Slide the buckle onto the watchband strap (with the pin facing outwards toward the ends). Bunch up some of the strap to allow the buckle some wiggle room. Punch a hole through the watchband strap, the runner strap, and the leather blank; rivet these together. Follow this same process for the other strap.

Step 8: Add a Watch Head

Add a nice watch head to the straps, tighten, and enjoy!

Step 9: Thanks

Thanks to everyone who viewed this instructable. If you have any questions on a step, please leave a response and I will try to help.

I want to say thank you to Tandy Leather Factory, where I purchased my leather supplies for this project.