Lasts are made one of two ways... expensive shoes have custom lasts made by last makers, or "modelistas". For those brands who can't afford custom designed lasts, or who are just not fashion forward enough to lead the way in shoe shapes- lasts are copied.
We as designers go out to the market and we shop for shapes that we love. If it's a wedge or a heel or a pump or whatever, we buy it and send it to China to have a mold made of it.
If its an entire shoe shape we want, they pour a sort of hardening liquid into the shoe and it makes the shape. Then, the last maker refines it and tries to make it as close to the original as he can. When we see it we'll sometimes tweak it a little to make it our own. It's all a crazy involved process. Same goes for copying heels. A heel maker will make a wooden carving to match the original shape and when we OK it, they will send it out to have plastic molds made for mass production.
After the last is to our liking, we start to make shoes on them. Pattern makers take the last and develop the upper patterns according to the shape and measurements of the last, along with standard measurements for footwear. Then, they cut the leather, send it to the sewers, then the sewers hand all the pieces to the lasters, and they "last" the shoe. Which means taking the upper and stretching and nailing/gluing the upper to the last. then the bottom is attached and the last is slipped out. Then your foot goes where the last was.
I hope this is all making sense?
They bring the shoe to me, usually in groups, and a fit model with standard measurements comes in and tries on the shoes. I then adjust the patterns to make the shoes look and fit the way they are supposed to. The shoe I posted yesterday was a "first proto" which is the roughest proto. You can see my notes on the shoe. I corrected the top line of the shoe with masking tape. You can see the new line I want cause it was too low before. Then you can see that I am making the two straps a little wider and curvier. I am also changing the last that this shoe is on to make the toe shape a little wider since this is for a junior brand. This shoe is cute the way it sits, but I think it's a little too sexy for our girl. I will probably see 3 or 4 protos of this shoe before approving it.
Crazy, right? This is what I do.