Silica Dessicant Tray & Brackets - FreeCAD Parametric

User trtr6842 designed the box and lid (598186), which are easy to print and function very well.
They helpfully provided a FreeCAD parametric model for users to create additional sizes. 
(If you only want a freestanding box then it might be simpler to begin with that original model).

My remix adds a pair of brackets, which can be screwed to a drybox lid or other flat surface. 
The box slides out for refilling, until which time a retention spring holds it in place.

Again, the FreeCAD parametric source is included. 
For those less familiar with FreeCAD, find the parametric spreadsheet in the model tree. 
If changing several parameters, it may help to “skip recomputes” beforehand, and then do a manual update once all done. 
The brackets do add some complexity to the source model, and make it somewhat less robust because certain combinations of parameters aren't valid. You'll probably figure out what does and doesn't work, but if it becomes an unsalvagable mess of errors then begin again with the last good saved model.