Buy some skees. or a snowboard and cut it in halve. Buy some metal tubes and fix the board / skies to your rear bridge & your fork.
Place a long pipe trough the BB shel and fasten it from 2 sides. flatten out the ends of it or if prefered weld a L/ R Pedal on to it. ( Not moveable just a tight flat surface )
There re some Youtube how to's and otherwise you can google for how to's