I used 4 layers of 8×8 cakes to make each block (1 box mix of cake filled two 8×8 pans). I just trimmed off all four sides to make a nice flat edge and used buttercream icing.
I used candy melts to make the letters and characters. Just melted them in a ziploc bag in the microwave and added my food coloring. Then snipped the corner off and traced my pattern on the wax paper. Make sure to use skewers in the baby blocks cake so it doesn’t fall over.