Before we used corn nesting trays inside yurts, we used wooden nesting trays in wooden structures (picture below). Here, we are dealing with thousands of cocoons. How to release them is a good question.
With alfalfa leaf cutter bees, cocoons are set out in open trays (see previous blog), bees emerge and then fly to nearby nests. I have tried this method, but gusts of winds or something upsets the trays and all cocoons end up on the ground.
The system I normally use for setting out cocoons is to place them into small wooden shelters as seen in this photograph. On the upper shelf in this picture there are 3 shelters on the left hand side and 3 shelters on the right hand side. Each shelter contains between 100- 250 cocoons. The little door on the front of each shelter has a hole from which mason bees emerge. I find this shelter system the most secure way of releasing cocoons, no matter how many cocoons I have.