Active job

Under house flooring for storage

I would love to get an floor/ deck / storage space built under our house. I'm not sure on the best design but would love to have a flat wooden surface - even if on a 2-3 levels. The photos show that we have just had insulation and a ground vapour barrier laid on the ground. I'm not fussed on how it looks, just looking for a solid/ cost effective build. Total area would probably be about 20-30 m2. Thanks, Tim