I had 2 dwarf gouramis that built bubble nests at the same time. It was pretty cool. They didn't realize there were no females. They built them in opposite corners of the tank and each would raid the other's nest to try to destroy it.
Basically they floated some small twigs in the back corners of the tank. Then they made a lot of sticky, foamy bubbles to fill in the holes. You can see them at the surface spitting these bubbles. I don't remember what plants I had at the time, but one of them had very thin, fluffy and delicate leaves. They would rip these off the plant, carry the leaves to the nest and shove them into the bubbles.
Unfortunately I don't have any photos
Good luck
