This was done last semester using a technique invented by Henri De Toulouse-Lautrec called painting with spirits or “peinture à l’essence” (don’t ask me to say it). It involves using oils on cardboard or paperboard as both a painting surface and palette. The board absorbs the oils and the paint dries fast so you have to work quickly. Because the paint dries so rapidly turpenoid (or odorless mineral spirits) is needed to add some moisture back into the paint.
Apple N Pear 
This sounds like an interesting style to try for something different. I like how you can see the corrugations in the background, but they don’t really show up in the parts with thicker layers of paint applied to it.
Thanks! This was an assignment and I got dinged for using corrugated cardboard. I didn’t know beforehand, but there’s something called paperboard which is cardboard without the lines. However, I kinda like the corrugation and that idea of painting on whatever cardboard surface is handy around the house.