I attempted to duplicate Native Union's BLOCK Wireless Charger with the Anker Wireless Charger I already had. Since my printer's print volume is relatively small (120mm^3) I cut it up with different join methods (tongue and groove or dowel joint) which turned out pretty good.
If you have a larger printer I included two files that only require the dowel joint.
Updated - Added photo of finished product. There's a bit of give in the ring around the charging pad. I don't find any problem with this when in use. If it bother's you though you may want to hot glue/super glue the joints in the ring to reduce the give.