Besides the evaluation grids proposed in the original publication by Hummel et al., other options for quick assessment can be helpful.
In particular, to cover a tracking volume of small field generators (e.g. the Polhemus TX-1) which also allow tracking in both hemispheres, it can be helpful to affix the field generator in the middle of the board and measure around it.

Here a 4x3 volume with 15 cm distances is proposed.