I designed this platform for my turtle, I use it in a medium IKEA Samla container, placed in a corner on the top of the container. To stop it, simply use bolts with nuts and washers. the size is 150x200 mm To have good rigidity we recommend a 15% filling I used the fuzzyskin cura function to make the surface rough

moved here: https://makerworld.com/en/models/208631