I used rope type weather stripping caulk to attach the collar to the freezer. It's sort of like a sticky modeling clay. The beads in the flat ribbon make it easy to rip to the desired width and you can mush it together at the corners and ends. It's also very easy to remove if need be later on for any reason. I used 2 x 6's for the collar which is fairly heavy. The freezer lid hinges are attached to the collar only, not to the freezer body, the same as marzsit described in the previous post. The combined weight of the collar and lid is sufficient to hold it securely in place. No adhesives, glue, screws or brackets were used or needed. The rope caulk is also very cheap and you can get it at Home Depot, Lowes or most any hardware store:
http://www.hardwareandtools.com/M-D-Building-Products-71522-Rope-Caulk-30-Feet-Gray-3439247.html
It makes a good seal and takes up the slack for any minor imperfections in the wooden collar. My converted freezer has been in use for almost 3 years and I've had no problems at all with the collar to freezer seal.