The following plans are for very nice wheeled planter boxes. The boxes don’t have to be on wheels (casters), but if this is right for your space, go for it.
These planters have a fantastic shape and provide a very contemporary feel. I could see these around a pool at a nice hotel.
The plan is relatively simple. The only real “tricky” part is the double angled cut on your inner frame to achieve the taper. To be hones, it isn’t that big a deal. In fact, you could achieve that angle with a bit of sanding, so don’t be intimidated by the taper!
Good luck building this nice contemporary, and portable, planter.