I am just trying to remove everything in my model (stl) below the cutoff, the pink-ish line in the image below. I want to do this because (1) it has that non-flatness/bump on the bottom and (2) it will save material and time for the 3D print. Or is there a better way to remove the non-flatness/bump? I anticipate it will leave a hole which also needs to be filled in. Or actually would that matter if I am just going 3D print this (after smoothing)? It will be solid, so 100% infill.
Google Drive link to STL file: