You can cut plastic into strips, but the bees will like the wood strips better... and won't care about the imprints and won't prefer plastic over wood...
I cut the corner off of a one by at 45 like Blue Bee. If I could find chamfer molding somewhere easily, I would buy that but it's hard to find for some reason. We used to buy it back when I poured concrete from all the local lumber yards but it seems harder to find now that they all converted to these "department store" formats instead of a real lumber yard.