Hi Sandra. Sometimes when I have made a novelty cake for family and wanted to give the illusion of a slightly deeper tier, I have put one or even two 1/2 ” deep cake drums the same size as the cake underneath it, instead of a thin board, and then incorporated them under the fondant covering. (I am in UK and not sure if they are widely available). Maybe this would not be acceptable professionally, but if it’s for family and you are happy with the depth for eating purposes, no problem. I did it with the bottom tier of the castle cake i recently posted. Good luck!