Is it normal for the icing to stick to the bottom of the cake boards when cakes are stacked? I have never had to cut a stacked cake and did so last night and the icing from the bottom layer all stuck to the bottom of the top layers board. Any suggestions?

Yes, I have had that problem. There is nothing you can really do when pressure is applied from the other cakes stacked and it sits for a while. My trick to not taking the icing off is I try to twist and lift at the same time so its not a direct pull off the cake. Every cake sets in it its own way, and for the cakes I have had that happen too. I have used my emergency cake kit to fix things up. Hope this helps.

You can use a circle of waxed paper.