You don't need to make or buy anything.
Use a long wrench, preferably 12-15". Put the wheel, with tire mounted and inflated, on the floor against a wall with the freewheel on the left, so that removing it would roll the wheel towards the wall. Stand over the wheel and set the wrench so the handle is horizontal or above pointing to the wall. Push down on the wrench, the wheel trapped in the corner, won't turn and the freewheel will come loose.
Don't forget to back off the nut or skewer immediately, before removing it once it's loose.
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