How do I move photos from my mac onto an Ipad?

This seems like something that would be easy--drag and drop--but it's absolutely impossible.

I have an ipad we're using for a work project, the ipad's only job it to be used as a viewer for a few gigs of photos, the photos are in a folder on my desktop.

I cannot for the life of me get the photos onto the ipad.

Itunes sync doesn't work, neither does the "photos" app on my computer.

All the suggestions online, from weird third part SEO sites, reference a feature that is no longer part of itunes.

As this is a single use thing, for work and not my personal stuff I don't want to get icloud or anything involved.

The fact that this isn't an easy, drag and drop process is maddening.