Building a greenhouse on a lot with fundation

Thanks all! For some reason I took it for granted that those plant boxes had to stand on the ground, so I removed the floor. This greenhouse is quite small, and adding stairs inside would take up too many floor tiles. Outside the stair is very nice. So, I'll just keep the floor - easy! :)

I'm building it only for herbs and a few small veggies. Don't mind bigger items like trees etc go dormant during winter.