It's slanted due to the stairs below, how would you utilize the space?
First thought was a tip out drawer, but that wouldn't be space efficient. I can only picture 2 pull drawers, what do you think?
I would go with just 2 shelfs, seems the easyest solution. Just put a board on the slanted part as a back. Make a smal shelf at about 20cm high, and a higher shelf with more depth above that. Then hide the bit under the bottom shelf and the beam/planks on top with a nice plank. As an option you could put doors in front.