Can I use a 0 mm top layer thickness in Ultimaker Cura to create an open box?
Yes that will work in Ultimaker Cura exactly as you say.

So if you have a solid model of a cube, you select wall thickness, bottom thickness, 0 % infill, and no top layers or top layer size of 0 mm. You will then end up with a box without a top layer, but with walls reaching up to the height of your model.