While there are a lot of good tile holders available on the site already, I didn't see any that were all squares. I don't know about the official sets, but the ones my kid has come with way more squares than anything else so I designed this to fill the gap in storage. This design holds approximately 60 of the 3 inch square tiles (or 120 of the right triangles), but I uploaded the step file so it can easily be scaled up or down to fit more.

Update: I've added a modular version including all the pieces my kid has, they can be chained together in a row infinitely long, but two (or one for the larger pieces) deep using the dovetails in the file. Note, to implement the modularity I had to go with a grid system so the smaller ones use a lot of extra filament.