Sketching on this lattice
A box is three parallelograms: a top face using the two 60° families, plus left and right faces that each mix a 60° family with the horizontal. Keep each edge on an existing line so the corners close. Fine 3 mm spacing helps small objects; 10 mm spacing is easier for first cubes.
The related triangular grid uses the same 60° families with a side-length control. Walkthrough: how to use isometric graph paper.