For 6 string builds, the box is filled with a solid piece of wood which is routed for the control plate and pickup. 6 stringers have lots of tension so the solid wood is structurally needed. If I build 3 or 4 stringers I use a "neck through" design without the chunk of wood since it's less tension and then those can be acoustic or electric.
I do not have vids of any others. I usually don't set them up to play slide since I'm not a slide player myself. I'm lucky enough to live right around the block from Martin guitar and get parts from them so I feel I should set them up to play regularly