Clear an area outdoors for your stacked flower-pot stand. Check to be sure it will be on level ground and then remove any weeds from the area.
Hammer a long piece of reinforcing bar (rebar) into the ground. Measure the length you will need by calculating the height of all your pots. Add an extra 2 feet to your calculations to account for the part that will be keeping the stacked pots stable in the soil.
Slip the largest pot on the rebar so that it sits flat on the ground with the stake through the drainage hole. Pour landscape rock into the pot. Fill it halfway up to provide a heavy base and allow water to drain.
Thread the next pot through its drainage hole into the rebar. Tilt it to one side and then fill 3/4 of the way with potting soil. Do not fill to the top since the pot will be tipped and the soil can spill out when watering. Part of the base of this pot will be resting on the soil of the first pot at a 45-degree angle.
Continue adding pots, tilting each one in different directions and angles. Fill with soil as you go.
Plant flowers as you fill the pots with soil, or wait until the structure is complete. Leave a section of the soil unplanted in all the lower pots so that the next flower pot can rest on it.