The slots are relatively narrow, maybe 2/3 of an inch. I think that you don't want the slot too wide because it would use too much solution, weigh too much, and the suspended print would wallow around and perhaps bend during agitation.
The surface of the inner chamber is dimpled, kind of like the opposite of a golf ball. I have seen some similar patterns on things like shower glass and cabinet door glass.
The clips are plastic, the ends of which slightly splay apart (like a duck's bill) when squeezed and the paper is jammed in. This slightly mares the edge so it is not good for borderless prints. Also, for prints larger than 11x14, two clips are required.
If you make one, it would be good if it drained easily. Slightly canting the bottom toward a spigot drain would be good. Also, it can't be moved when full. A small aquarium heater and pump might suffice for the water slots.