To keep the delicious but runny cherry pie filling from squishing out the sides of the cake, I piped a thick ribbon of fudge frosting (using a decorator bag fitted with a fat round tip) around the inside edge of the cake first.

Make sure the frosting you use is stiff enough to work well as a barrier. Store/canned frosting is too soft. Once you spread the filling inside the frosting barrier, place the next layer of cake on top and refrigerate before frosting. This will give things a chance to firm up a little so it’s easier to decorate. 

Here’s another example using a sheet cake: