Just set one item of each of the craft in the crafter and will only produce shulker boxes when the barrel is empty and when there are extra materials in the hoppers so that it does not become unconfigured.
Schematic link:
https://www.mediafire.com/file/blqmz10663pcj7f/Shulker_Crafter_2x5x5.litematic/file
by Numerous_Interest800