Measure one of your shoes and scale the sole accordingly. I am a size 9-9.5 and I scaled it to 11.5 inches long (each piece 6 inches long when split). Print the sole and remove support material. If printing in two pieces, slide them together, applying a strong adhesive (Krazy glue or something like that) to the slots and seam. Sand down any sharp edges. Cut the upper part of the shoe out of a strong and flexible fabric (I used a scuba suit material I bought from a Jo-Ann fabric store). I attached a .jpeg that can be used as a stencil, the length of the fabric from toe to tongue should be about 75% of the overall length of the sole, so scale accordingly. Apply strong adhesive to the edges of the fabric, attaching it to the sole. Run zip ties or laces through the holes in the sole to tie shoe. Cutting out an insole from a material of your choosing will also increase comfort.
Sole should ideally be printed in as flexible a material as possible.