Rotary tool or wood carving tools
Ponytail holder, or thick rubber bands (2) (optional)
1) Procure a small tripod if you haven't already. I used the flexible tripod that came with my Flip video camera
2) Find/cut a flat piece of wood that is slightly longer than your phone, and is thick enough to cut about 1/4" into it without compromising its strength. It also needs to be about 1.5" in diameter.
3) Make marks near the edge of the wood where you'll cut the "trench" that will cradle your phone. Don't get too exact with your markings, because unless you are a master with a rotary tool you may have to wing the measurements a bit. (Keep in mind small things that may effect the size of the cut, like wether you have a skin case or not)
4) Measure about 1/2" from the edge you are going to cut your trench and drill a hole a third into the wood to allow you to mount the adapter to your tripod snugly. Do this first so you don't cut too far into the wood or risk splintering the trench and then have to boar it out.
5) On the side opposite of your new hole, cut your trench. To cut the trench on mine I used a simple cutting head and rounded grinder on my Dremel. If you are making this for a iphone 4 you may want to cut it out by hand or use a router since the angle of the edge is so straight.
6) To make the support backing, angle a 45 degree cut off the other side of the wood block, and then glue the flat side to the edge of the trench.
7 opt.) Measure the very middle of both long sides of the block, then make a mark 1/2" away from the middle on the right and left on both sides. On both sides make two small niches to keep your securing bands from moving around. (Optional if you have a better idea on how to secure your phone to the wood, or feel comfortable with how snug you were able to make your trench)
From this point its all accessorizing and decorating. If you were curious, to make my finish I spray painted it black, sanded off most of the paint leaving small blotches, then put on a cherry varnish, then sealed it with semi-gloss polyurethane.