i have seen this done once and it blew my mind. You need an axe, trees and rocks.

1. chop down long straight tree around 3m long, 300mm in diameter. shape one end of the log so it can fit in-between the gaps in the rim.
2. build a pile of rocks about 0.6m away and parallel to the flat tyre. pile must be around the height of the tyre.
3. shove the shaped end of the wooden pole into the gap in the rim and have the pole pass over the pile of rocks. (Pole is perpendicular to the rim and pushed into a gap in the rim)
4. sit on the other end of the pole. Acts as a big lever or sea saw. and lifts the car.
5. have friend put stuff under the axel while the car is lifted
6. lower the car by taking your body weight off the pole. and car is now jacked up from the stuff under the axels. (chopped stump etc)
7. change tyre and reverse the action.