I just did this cake. I used my poundcake recipe. I did 4 blocks that were finished to approx. 4 1/2 inches squared. I baked a 1/2 sheetcake and cut my blocks out of it. Only because the sides of this pan are straight.
After icing the blocks I covered them with fondant. I could have mitered my edges better. But, I was the only one that noticed them as not being perfect. Create a template for this and you should get pretty good results.
Also, I covered each side with fondant individually and was able to get it very thin for this reason. I personally do not like thick fondant.
This cake was cut down the middle and then in four slices. So the slices were approx. 2.25 x 2.25 x 4.50 which is a very generous slice. This was done because only cake and punch was served at a 4:45 p.m. shower.
Check out my cake in my photos.