yup..ya mount antlers too the backing board like your link. Then he used some heavy cardboard tacked to the side of the backing board to give it the outside profile shape. Basically it makes the bowl so the foam isnt going everywhere. Spray it, file it to shape, cover with leather and mount it all to your favorite plaque...nothing much different then the link you posted other then the foam spray instead of paper mache or plaster of paris. They used it on moose racks up here as the plaster of paris is heavy, as is the moose antlers themselves. Spray foam is LIGHT and easy to fix if it gets damaged.
You could also just buy the foam antler mounting plates from vandykes. they look almost like a euro mount........basically screw your antlers to it, cover in foam or plaster of pairs again, file, cover with leather, mount to a plaque or mount to the wall as is. Pretty simple and easier yet...there is no backer board needed as it's already part of the foam head. Something you can build on your own once you have one using the spray foam and a piece of plywood for the backer board. YOu'll need to make some kind of form for to spray into...nothing terribly difficult though.