Assuming you use a drill press and fence, you could index with two pegs set into a square board. Center the hub hole on the square board, insert peg and glue it in.
Place wheel on peg.
Drill first wheel hole through wheel and board, insert 2nd peg into the wheel hole (no glue) and the board. Rotate square board. Drill again. This will yield four holes. If you need 6, you’ll need to cut a six sided board.
Another 6 hole method would be to take your square board and draw the X to find the center, as you would have done for above. Then draw lines at 60 deg from one leg of the X, intersecting the mid point.
Drill and insert peg in the middle. Place wheel on peg. Now, you can transfer the lines on the board to the wheel and use those lines to indicate where to drill the 6 holes. In this case, you’d rotate the wheel, not the board.
To add precision to the second method, drill the first wheel hole though both the wheel and board, remove the wheel, drill a second hole in the board on the next line (60 deg. left or right ), insert loose dowel peg, then replace the wheel, sliding the first wheel hole over the loose peg. Then you can simply repeat for the next 5 holes.
-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton
