Twice lengthwise; 3 widthwise. The original Pocket Boxes were 4" x 7" internally; the maps were 21" x 32"; so to make them fit, the maps were folded in half widthwise, then S-folded lengthwise, then W-folded (or "accordioned") widthwise.
(And if we're ever at the same con, I'm available for autographs. ;) )