My shower base squeaks when I use it. What can I do short of removing it to fix it?

It makes noise because the installer did not bed it correctly. Can you get at the base from a room below by drilling a few holes up through the sub floor?

One side and the back is open still. The walls on those sides are not up yet. The other wall is to the outside of the house.

You need to pack the space below the pan with thinnest. You can thin it to the point that it is pourable or even pumpible

The one thing you don't use to bed a shower us the foam that comes in a can. It's mostly air bubbles that will compress leaving you in the same situation. Good luck, Tom

Toms right. I did try that once and remember there are two types of foam. I knew not to use the insulation foam because it expands and will raise up te pan in the middle. I tried minimal expansion foam and over the years it compressed, squeek came back

You need to pack the space below the pan with thinnest. You can thin it to the point that it is pourable or even pumpible
Would I need to put plastic film or something down first or could I put it directly on the felt the base rests on? If I can do it without removing the base what kind of pump would I use?