I built this shelf with these brackets: https://www.printables.com/model/219493-stick-to-wall-shelf-bracket

Made it to take up the whole printing surface of the Prusa i3.

V1 (the one in the picture) ended up a bit saggy in PLA+. V2 was scaled on z axis and V3 is smaller and doesn't have the side bands.

Can be scaled on x-y axes to fit your needs.

Future improvement: implement Lissajou curve in Blender geometry nodes,  to control the shape parametrically.