I'm so sorry. Somehow I totally missed this post. For I surely would have answered you right away.
There are at least two different ways to do this. Each works... you decide which is best for you.
1) place your doily on the board. Place foil or saran wrap or even paper towels around the outer edge of the doily enough under the cake area - about 1/2-1 inch only. Decorate your cake. Before adding your bottom border, remove the protective barrier. Finish decorating.
2) Using a different cake-board that is the same size or less than your cake, decorate the cake accept for the bottom border. Place your doily on the presentation board. Using a long offset spatula, lift the cake from the turntable and place on the presentation board. Finish decorating.
Good luck! BTW, I prefer the second method. But I have a friend who swears by the first method.