When I did this many years ago, I used masking tape. Blu-tac sounds like a good option, if you don't have a big vacuum board or magnet strip setup.

If you've got room for floor projection, the basic technique is to reverse the enlarger column and turn the enlarger around, weighting the baseboard, so the enlarger doesn't topple over. Some enlargers like Omega D's can do this easily. Some require unscrewing the column mount from the base and putting it back with the head facing the other way, and I suppose that for some enlargers, there may be no easy way of doing it.