Anemones foot/basal disc is very flexible. Trying to make it stay put will either injure the animal or they will just ooze out - this is one of the prime reasons anemones are tough to work into a reef tank scenario.

I can give you this advice for LTAs - dig a small depression in the sand almost to the glass - place the anemones foot towards the depression and line the area round it with small rocks and place a chunk of live rock over part of the foot towards the back but not so it's pressing on it. He should attach to the glass and stay put after that.

FWIW bubble tips seem to be about the best for staying put once they find a spot to their liking.