It is much easier for the beekeeper to remove the honey crop if the density of bees in the supers is reduced.
Some people expect the supers to be completely free of bees… Whilst this can be achieved it takes longer and requires more than one visit to the apiary.
I have always worked on the principle that the method should only involve one visit and should not involve a “waiting” period.
In my particular case I have apiaries with between 12 and 40 colonies. Those apiaries that had large numbers contained various colonies that were used for breeding or were developing colonies that had no surplus. There was never more than about 30 to deal with at once. Most of my clearer boards are triangle escapes.
Specific dimensions for the boards themselves are not given as this will depend on the type of hive in use and whether top or bottom bee space has been adopted. General construction is a sheet of exterior grade plywood with overall dimensions the same as the hive with a rim on top and a rim underneath that can be anything from 3/8” to 1”deep.
I usually give the wooden parts a coat of linseed oil (there is no need to “Vaseline” the rim as the board will not be in position more than a week.
The technique is simple… A quantity of escape boards (at least one per colony) is taken to the apiary and they are positioned under the supers to be removed. Start at one end of the apiary and proceed to the other fitting boards as you go. I return in 3 days, The supers will not be entirely empty, but the majority of bees will have left.
If you are prepared for a little extra work there is another method that is more effective in reducing the bees left in the supers. This requires a little preparation and also you need to have a hive stand, floor and spare cover for every hive to be harvested. first place a stand and floor (with escape board directly on top of the floor) about one metre behind each colony with the floor entrance facing away from where you will work the hive. Also place a spare cover in easy reach of the main hive. Do this for every colony to be harvested. When all spare equipment is in position start at one end and transfer the supers of the first colony (en bloc) to the escape board and quickly cover the brood box with the spare cover. Repeat this process until all colonies have been dealt with… If you return to your starting point you will find that a significant quantity of bees have flown back to their respective colonies leaving only a small number.