The boot heel should not have slip in it.That is one of the things you look for when you buy boots.Some stores have a ramp you can walk up and down when trying boots.You may be able to experiment with lacing tension to stop the heel slipping.Possibly a little more tension toward the top-not too tight though.
The blister pacs are a good idea as are the poly liner socks with heavy socks over.It is a good idea to carry an extra set with you everyday and partway through the day,take the wet ones off,let your feet dry,check them for blisters or hot spots,treat them if needed and then put on the fresh,dry socks.
Do not wear cotton socks.
Take the time to take care of those feet.The outcome of your hunt may depend on it.