I've been baking and decorating for three years now. Just recently, I've come across this issue TWICE and I'm quite perplexed. Never, before now, have I had a cake (the whole cake) slide on a board during transport. For both of these instances I used corrugated boards covered in fancy foil (my norm for single tier cakes). I've never put buttercream on the board before placing the first layer, but after the last incident, I decided to give it a try - to no avail. The buttercream icing is medium consistency, crusted to the touch, and the cake cuts and slices perfectly fine. I haven't changed recipes and I'm just at a loss. I am in Dallas and the temperatures have been warm, but not overly hot and transport hasn't been especially lengthy. Any thoughts?

ACould try royal icing to stick it to the board as that is stronger

Try to put your cake on a cardboard cake board with a dollop of BC icing, then place the cake on the foil covered board with some double sided tape or packing tape inside out. The tape will secure the cardboard to the foil board.

AYou could also use a little square of shelf liner under your cake circle, look for something thin.

I had that problem before. I use two boards, one the size of the bottom tier and a bigger cake drum for the whole cake. I put a little dollop of buttercream on the cake board before placing the bottom tier cake on it. Then I put small pieces of fondant in a circle shape on the bigger cake drum for the whole cake to sit on. The weight of the cake and that fondant on the bottom helps it to not move. Then when I transport it, as someone else suggested, I put down the shelf liner on my seats to further prevent slipping.  (I hope I'm explaining this clearly.) This really helped my issue.

I always put quite a bit of bc on the cake drum (what I always use for the bottom "plate").  Not a dollop, not a little smear - a good bit. 

Thanks everyone. I appreciate your insight and will try some of your suggestions.