I had cut off part of a plant to propagate it. To grow roots, I put it inside a little glass mug filled with water. However, the plant would only float sideways and the leafs would be inside the water all the time.

This print fixes it. We can simply fiddle the lower part of the plant through the hole, so the plant looks straight up. The part where the root will grow is now below the plate. Put it on a water surface and it floats around, submerging the lower part of the plant so it can grow :) With the green it also looks really cool.

FYI: this is just a cylinder with a smaller cylinder as a hole, you will probably need to make your own version to fit your plant.