There's a few more details here than other versions, but others are worth the read.
The original industructable is here. Check this site, though, for the granddaddy of tire sandal pages,though.
Step 1: Cut the Tire
I used a reciprocating saw to start with. Keep pouring water on the tire to make it easier to cut. Most tires have metal bands on the insides--you'll have to cut these out first.
Use the saw to cut across the tire first, then cut the bands out. If you get a wide truck tire, I recommend cutting the sidewalls off too--they get in the way and you'll have to cut them off anyway.
Make a pattern using a shoe that you like--make sure you've got plenty of room on the sides of your feet--you'll need 1/8-1/4" later.
Cut off a piece of the tire a bit larger than your pattern.
Step 2: Cut Out Your Pattern
I tried using the reciprocating saw for this step, too. It works ok if you have a good way to clamp down the piece you're working on so it doesn't vibrate.
I didn't have a good way to do, so it ended up being a huge hassle and very difficult to be exact.
Using a chisel is less work (although it takes a lot longer), and you can be a lot more exact.
According to the big tire sandal pagebig tire sandal page, using a bandsaw is just as hard or harder as well.
Step 3: Cut Holes for the Straps
You'd be suprised how tough the tire is, so you can really get away with getting really close to the edge (granted, I'm not sure how mine will wear, but I'm not worried about them at all).
Then, using a utility knife, but the tread out from the strap hole to the edge of the sandal. This keeps the strap off the ground, at least a little bit, so you're not walking on it.
You might want to also use your utility knife to enlarge the strap hole. The hardest part of making these sandals is pushing the straps through, so cutting a little extra probably wouldn't hurt.
Step 4: Install the Straps
You need to cut the stitching on the leash so you're left with a straight strap.
Then get a tiny screwdriver and a decent-sized flathead. Use the tiny one to wedge open the first slot for your straps and the flathead to push it through.
The toe strap should run down into the sole, then come over and across. If you do it the other way, it's really difficult to adjust the toe strap when it's on your foot--you have to take your sandal off to adjust it.
I got both sides of the toe strap pushed through, and adjusted to what I thought would be about the right length (it's one piece that runs around my heel). Then I cut the strap and pushed the remainder through the heel slots. I left the heels strap uncut till I sewed the buckle on.
Step 5: Sew the Straps
I sewed the buckle on the large strap first. Then I ran the strap around my heel and clipped it, then cut the heel spacer straps. These straps are basically just loops. They're NOT the same length, b/c I wanted the strap to avoid the bony parts of my ankle.
I pulled the outside of the spacer strap up to the heel strap, then pulled the inside up, over the heel strap and down, then sewed through it, so I ended up sewing through 3 layers.
I made these a little longer than they should have been, which works better than making them too short, since they pull the heel strap down if they're too short.
Step 6: Done!
Here's one more link for another designanother design. I haven't figured out how to do this with webbing though. And boy howdy does it look involved.