The following is a tutorial I wrote in 2006 on constructing elevated shoes.
This is a good way to add eight inches to the height of a costume. I built them to become a tall wizard for Halloween. The concept is simple. Glue four layers of two inch thick foam to the bottom of a pair of boots. Cover it all with fiberglass. The foam/fiberglass combination is both lightweight and strong. Add a rubber sole and two lateral steel bars for support and you will soon be standing--and walking--eight inches taller than you actually are.
Start with an old pair of boots that fit--I bought mine at a thrift store. Buy a sheet of R-Max insulation. It is designed for insulating building walls, and comes 2” thick with aluminum foil coverings. It is a urethane foam that is rigid but lightweight. Trace the boot sole onto the R-Max and cut out four layers for each boot. I used a bandsaw. Shape the upper layer to fit under the boot sole fairly closely. Glue it onto the boot using hot melt glue. Glue on two more layers that are full thickness. Add a fourth bottom layer on which you round off the heel and the toe..
In normal walking your foot flexes as you walk and your toes bend. In this elevated shoe everything is rigid, so you need to round off the toe to make walking easier. Same for the heel, although not as much as the toe. Cover the outside of the foam with two layers of fiberglass, continuing up onto the sides of the boots. The foam by itself will simply break apart once you start walking on it. The fiberglass will hold it all together.
Carefully walk in the boots to check the roundness of the toe and heel. Once you have them shaped how you like them, glue on a piece of sheet rubber to act as a sole and to protect the foam from breaking on the bottom.
Now you will need to add lateral supports to keep your ankles from bending sideways and potentially seriously injuring yourself. They need to be strong enough not to bend. I used a shelf standard--the kind that is shaped like a ‘U’ and has slots in it to hold the shelf brackets. They are available at hardware stores. You can hacksaw them to the proper length which is just below the knee.
Attach the lateral supports to the boot by means of two bolts running horizontally from side to side through each boot in two places (see diagram). Fasten them with washers and nuts. Rivet on a nylon or leather strap and buckle near the top to hold the lateral supports closely to your calf.
It's a little scary at first until you get used to it, but you can become quite comfortable walking in the elevated shoes.