The first technique is Gelli printing. This can also be done on fabric using either acrylic or fabric paint.
This was my gelli plate that I "ruined" trying to print with thickened dye. Don't try it. I remelted the gelli and it ended up looking like confetti. I used a knife to cut a rectangle the size of my page (4.5" X 6").
Stamps, paint and a brayer
I chose the green to visually pull these two pages together
This page was printed solid yellow with a gelli then I put orange on the gelli plate and stamped it with this stamp which removed the orange on the stamped bits.
Then I stamped the opposite page to bring the tiny square elements on the pink to bring the pages together using similar elements.
When I was done I had a bit of the green paint left on the brayer so I just rolled it onto a page as a first layer.