Creating Humanoid-like parts?

Hello DevForum, it’s been a while!
I’m currently building my own fighting game, right now designing an attack in which the player hits the opponent with a giant fist. However, I’m not sure how to make normal parts look like the parts inside of a Humanoid R6 rig. Does anyone know how to make parts like these?
Thanks!

Im not sure you can make it in studio, you can try using blender, making a rectangle, bevelling and smoothing the rectangle until it looks desirable, im not sure how else.