My camera is a Nikon Cool Pix P100 and I was able to just hold the camera directly against the eye piece of the spotter. The frame of the camera will contact the rubber of the eye piece with no glass touching. It is pretty quick and easy.
I've had cameras in the past where you had to kind of "float" the camera behind the eye piece and that's a pain to get everything lined up for the shot.
Terry H had an idea of cutting a card board tube the length you would need to bridge the space to allow you to hold the camera up against something to get away from the "floating" problem. It sounds like it would work.