How to make a small patch to a plaster ceiling?

Question

Earlier this year, we had some electricians do some work on the house, and when they did, they installed a new ceiling light fixture (including a new box). Unfortunately, they left a hole in the ceiling adjacent to where the box ended up. The deepest part is about 3/4" deep and 3.5" square, but the damage to the ceiling covers about a 6" square area in total.

Here's a version of the picture with the three different surfaces within the hole highlighted and detailed:

Obviously, I'd like to patch it, but I can't figure out the right way to do it. I tried affixing an adhesive patch kit to the slats around the hole, but the adhesive wouldn't hold. I tried drilling into what I thought was solid wood at the base of the hole—turns out it was just some sort of smaller wood piece, not secure enough to anchor anything into.

How should I go about patching this hole up? I'm a very novice DIYer when it comes home stuff, so basic steps are greatly appreciated.

Answer 1

The easy way. Get a piece of drywall the same thickness as the plaster. Local drywaller might have a small piece, saves buying a full sheet.

Make the hole bigger so all four sides have something to screw the drywall in.

Tape and mud to make the edges smooth and prime/paint. New paint will be visible as a patch.

The harder way.

Make hole bigger to find the other slats on the other side.

Clean out the old plaster in the slats you see. Replace with new slats to cross the hole.

Buy some plaster, mix or ready to use and fill in the hole.

Prime/paint.

General info from a non plasterer.