First off, you should probably try this method on a cheap pair of flip flops at first, so you get a feel of how to do it before going and punching holes in that $300 pair you bought on your Hawaiian vacation.
And second, be prepared for a LOT of people gesturing at your feet and yelling "What're Those?!!?"
Step 1: So You Got Some Flip Flops.
So, you got yourself some flip flops. But... They're ugly. I mean, look at those sparkles on the thongs- those are just not manly. And besides, the little thingy that goes between your toes? That thing always irritates the crap out of your toes!
So, what are you going to do now?
Why, MODIFY THEM, of course!
Step 2: First Step: Destroy the Ugliness.
Yep! Those thong thingies need to go. So cut 'em off!
Then burn them.
Step 3: Sizing Your Foot
Now that those horrors are gone, it's time to get back to business.
Time to measure your foot to the shoe.
Take a permanent marker (or just any marker, I don't care) and make two dots near the base of your big toe. I'd recommend a spacing of about a centimeter apart.
Step 4: More Sizing
Next, mark two points just as before, only this time at the base of your pinky toe. (You can't really see the second mark because of the glare, but it is there.)
Step 5: Even More Sizing
Almost done now!
Now mark two dots, same as before, only this time place them near your ankle.
Step 6: Last Bit of Sizing!
Yep, this is a pattern. You're so clever for catching on!
Now mark two dots, a centimeter apart, near the base of the other side of your ankle.
Step 7: Punching Holes
Now, take your 4mm hole punch, and, you guessed it, punch holes wherever you made a mark in the previous steps.
One thing to note is that if you're using a punch like mine, you should probably put a scrap block of wood underneath so you don't end up putting holes into the surface of your work table.
Step 8: Careful!
Oh, and when you do punch your holes, make sure they aren't too close to the edge, or the end up looking like that hole in the picture.
If you do on accident punch a hole to close, then simply angle the punch sharply towards the inside of the 'flop, so it gets a bit thicker down at the bottom. If nothing else, though, you can always punch a new hole.
Step 9: How's It Look?
Well, if you've been doing the steps more or less how I told you, the it should look more or less like the picture above.
Step 10: Time for Threading!!!
So now that you've punched your holes, grab that paracord that you've been keeping handy.
1) Start by threading up through the first hole by your big toe. Leave about 3-4 inches of spare paracord out above the shoe.
2) Then, take the other end, and go up through the other big-toe-hole.
3) Now cross over the flip flop diagonally, and go through the first hole on the right side of the ankle. Make sure to leave enough slack for your foot to go between the paracord and the 'flop.
4) Next, go up through the other right-ankle-hole, take the paracord loop you made in step 3, and wrap around that loop 3 or 4 times. Should look something like the pic, believe it or not.
5) Being careful to leave enough slack, say three or four inches, go down through the back hole on the left side of the ankle. You'll know you have enough slack when you can pull the loop to about where the back of the flip flop is.
6) Now go up through the other left-ankle-hole, and, to match the other side, wrap around 3-4 times.
7) Taking the end of the paracord, cross over the entire flip flop and go down the back hole near your pinky toe, again leaving enough slack to slide you foot beneath the cord.
8) Go up the last remaining hole, and you're finished with this step!
Step 11: I Lied! There's a Bit More Sizing to Do.
Yup, you read the title right. But I promise this really is the last sizing bit :)
Put your foot into the loops, take the two loose ends of the paracord, and pull. It might take a little more wiggling and maneuvering to get the strings all tightened, but you'll know it's tight enough when it's comfortable on your foot.
Step 12: Finishing Up
Now simply tie a square knot (or any knot you want) with the loose ends, and trim them down to a manageable size.
Step 13: Glory Pics
Congrats! You've finished your first Moses Flip Flop! Now just go and make the other sandal the same way, and you're good to go.