Using the drying basin to get leather from flesh is undesired in the modpack I'm working on. Is there any way to disable this?

Yes, you can override the drying basin convenience recipes xml file in which the leather recipe is defined: https://github.com/CyclopsMC/IntegratedDynamics/wiki/Recipe-XML

Aha. It appears that it didn't automatically create that folder. I'll go ahead and do so manually, then give the recipe removal a shot using the _override subdirectory, as suggested.