I have some comments to make about creating your own last out of a foot casting. First, I wouldn't recommend casting your foot in a full weight bearing position. It produces a sloppy shoe. I have two sets of lasts from that sort of casting and I've modified them a lot to try and solve the sloppiness. It is much easier to make a different sort of casting to produce a better fitting shoe. The casting information for the full weight method is on this page -> http://norisstuff.co...waining/page/2/
After a bunch of trial and error, I've figured out a better way to make a casting for a last. I used a plaster bandage to wrap the ankle and the foot but not the toes, covered it with a plastic bag and then wrapped it with elastic wrap to hold it tightly to my foot. I was very careful to keep my ankle and foot correctly aligned with my leg and my ankle at 90°. I pressing only the forefoot into the floor with only a small part of my total weight until the plaster cured to leather hard. The more heel you need on your shoe (my goal is NO heel for a healthier foot and ankle), the more you should lift the heel off the ground when wrapping and curing. Full details with pictures are here -> http://norisstuff.co...ry/cordwaining/
You will need a mold release. Olive oil works but doesn't truly seal the plaster which lets it suck water out of the plaster you'll use for the casting. Glycerol with alcohol works better. You'll need to use two coats letting it dry completely between coats.
When the casting has set, peel off the original plaster wrap and set the casting aside to cure. When it's completely cured, use modeling clay to fill in the toe area for your shoe. If the casting isn't tall enough, fill in the top. You'll need to mold this newly shaped last. That's a whole other exercise.