And how does interference occur between "particles" that are larger than the "double slit".

Search the terms: "Young's double slit" on www.google.com and you will find several as well as other links.

It all started with Young's classic "double slit" experiment which you can do a search to find the details.

It has a strong resemblance with the interference pattern generated by a laser beam behind a double slit.

In the case of the double slit (or other "double" experiments").

The ears were mere holes, the nose a double slit, and there were no eyes at all.

The quintessential example of wave-particle complementarity in the laboratory is the double slit.

A double slit like a cross with four thin lips served as a mouth.

Does this "shed light" on the double slit, or vice versa?

Light passes through double slits and onto a screen resulting in a diffraction pattern.