Finally finished with Marceline's axe bass guitar! I started it on Monday (6/6) and finished this morning. I made it out of insulation foam, sanded it, gorilla glued it, painted it, and detailed it all by myself. This is the first prop I've ever made for a cosplay and I'm very happy with how it turned out. Stay tuned later this weekend for pictures of my complete Marceline cosplay!
EDIT: A quick summary of how this was made-
I used the pink insulation foam from home depot, shaped it with a saw, glued it together with Gorilla Glue, let it dry. I painted it with Mod Podge (gesso), let it dry, paint it with acrylic. The strings are just silver elastic that you can buy at any craft store. The nobs are painted bottle caps. The tuner prongs on the top are just little wooden nobs that I bought at a craft store too.