How would I go about making a cake into a cube or block shape like for a baby shower?? For some reason I am having a hard time figuring out what pans to use to begin with.

Squares stacked on top of each other?

Three 2in layer 6in cakes would make a 6in cube/block.
Four 2in layer 8in cakes would make a 8in cube/block.

I made a blocks cake once, It helps a lot to keep a ruler nearby. Depending on the size of cube you want, start with a square cake pan that size if there is one, or you cut the cakes to size. I made 5 inch cubes, and used 10 inch square pans. then I carefully measured and quartered the cakes so each pan produced four 5 inch squares. then I leveled the cakes and for me they ended up about 5 by 5 by 1 inch I think. Mine had buttercream in between the layers so by the time I had them stacked, four layers high, the buttercream filling made up the diffference. Then I covered them in fondant and decorated. Just as you are stacking the layers, make sure that they are adding up. If you need to make the top layer of cake a bit thinner before you put it on, that is possible, or if you are not getting quite as high as you wish to, you can trim down the sides of the cake to match the height if need be. Hope that makes sense and helps!

Here is a pic of the blocks cake I made. The fondant is really wavy in it but that is because the buttercream recipe I tried out for the cake was way too soft and not a good combo with the fondant. I also did not have quite enough fondant so it is thin and shows problems even more. But hey, they were cubes!

If you are not using buttercream, or depending on the dimensions of the cube you are going for, you may have to cut your layers of cake thicker or thinner. If you are making one huge block, like 8 by 8 by 8 or bigger, make it two multilayer cakes stacked to look like one but divided by a cake board. Put dowels or supports in the bottom half. Sorry to be long winded.

Here is a baby block cake that is made with 6" square cake pan. Each is 3 layers, each layer being 2". thus 6"x6".
Just remember whatever size you choose, length, width, and height will have to be same, to create a good cube shape.
A 6" block does not sound big, but in the end they are quite large.
If you are looking for something smaller. you can use 8" square pan and cut down the center both ways, and have 4" pieces, if you do not have a 4" pan.


http://www.cakecentral.com/cake-photo_1206810.html