Step 5: Start weaving the sandal!
While I can't tell you how to weave the sandal specifically, make sure the wrap is very, very tight around where the shoe starts. I tend to wrap each rope individually, then weave through the strands to hold everything together.
Eventually you'll start doing an over-under-over-under weave across the four ropes that make up the body of the sandal. Even though the two middle ropes are side by side at the start, as you continue to weave, they'll pull apart and tighten the shoe.
When you get near the end of a length of twine, tie off another one to it in a square knot, then cut off the excess and keep right on weaving.
As you finish each line of weaving, use your fingers to push it down as compactly as possible to the rest of the twine! The entire integrity of the sandal depends on this and you must pack this together as tightly as humanly possible or the shoe will fall apart when you attempt to tie it. The first pair I ever made fell apart because I did not pack enough twine into the sandal.
When you get to the side loops, wrap the twine around them several times before continuing to weave, making sure that this whole area is securely packed. If not, this is where the sandal will fall apart as this is the area where it's under the most stress.
Continue weaving until you get down to the heel area...