Is there a specific cake pan that anyone uses to make baby blocks or a small square? I have to make a cake that has two square cake presents on top of it.

Couldnt you just make them from RKt and cover in fondant? Just a thought

Depending on the overall block size you are going for, I would suggest using a square pan (at least 9x9) and cutting it into thirds for stacking.
Thirds both directions will give you nine 3x3 pieces, fill and stack the necessary number of layers needed for a square 3" high.

Obviously this is just an example. You can change your cuts, size of your pan, etc, depending on the final block size you are wanting.

The one in my pic's I baked in 1- 10" square pan and cut it in 1/4's, fillled and stacked.

HTH