We recommend drilling holes in an equally spaced diamond pattern around the entire log. Each hole should be about 1" deep and about 6" apart in rows along the length. Space rows about 2-3" apart, this should make the holes about 3" offset diagonally. It's okay if the rows are little uneven! You can reference the diagram below:
For sawdust spawn use a 7/16'' bit (12mm) and for plug spawn use at 5/16" bit (8.5mm)
Find instructions on these inoculation methods here for sawdust spawn and here for plug spawn.