Electrophoresis boxes are easy to make but pretty expensive to buy. They are nothing but electrodes in a box. I also created a separated box for pouring the gel with a comb to make the wells in a gel.

For proper measurements I just roughly copied the size of commercial units.

Electrophoresis Image 0

Diagram: schematics of an electrophoresis box.

Image: design in Fusion360 ready to be printed out.

Image: printed result.