PS Above assumes that the frame section is removable at this point and that you’re building a CLC kit. A combination of epoxy and 3/4 x 3/4 strips on all sides might do the job, and some stainless steel screws might be useful in that process.
I’m not clear from the picture where you are in the building process, what the big sheet of plywood on the bottom is, or how you broke the frame section, although the BFH in the foreground provides a clue to that.