Oil that had dripped from a bottle of vegetable oil got on the shelf of my kitchen cupboard. I didn't notice it then put a tray on top, several months later I find a sticky mess under the tray. Is this a botulism risk from any possible spores on the shelf with oil under a metal tray? I didn't store garlic or anything else there.
The environment you describe is not oxygen deficient and therefore not favorable to botulism growth. Simply being under a tray doesn't make an oxygen-free environment.
Plain oil provides almost no nutrients to support bacterial growth. You need another food source for bacteria to grow in significant number.
But let's take the worst case scenario and assume you've got a big botulism farm going on under that tray. Fine, clean it up with a sponge and some hot soapy water, or any of the many antibacterial kitchen cleansers that are available if that makes you feel better. Your botulism farm will be washed safely down the sink along with all the spores they produced. Toss the sponge in the dishwasher for a cycle to make it Felix Unger clean.