Using railroad spikes for legs
Form a ball of hypertufa mix in your hand and then flatten it to about a 1/2" thick; place it on the top of the mound. Continue in this fashion, working from top to bottom until the entire mound of sand is covered. As you add each patty to the sand mount, smooth the edges so that the patties blend together. Gently pat the mix to help form a solid surface. If you want a thicker pot, then don't flatten your patties as much. And if you find your pot seems too thin, then you can always add more mix while it is still wet.
Step 7 - Forming the Base of the Planter
Once you are happy with your pot and it's thickness, you can begin to form the base which will hold the railroad spikes. Since this planter will have three legs, I formed three thick circles at the top of the mound and then flattened them with a small piece of plywood to make them level. They are at least an 1-1/2" thick at this point. Using a metal file, your finger or some other round object, put a drainage hole in the center of your pot between the three circles.
Bonus Tip: To make sure your pot sits level, place a small piece of plywood on top of the mold and check for level. Do this again after the railroad spikes have been added. You can eyeball it of course, but I like to get things as precise as possible when I'm making them for the first time.
Step 8 - Attaching the Railroad Spike Legs
Now for the final touch. Place each railroad spike in the center of each circle you made, angling them outward as in the picture shown to the left. Press them in about an inch or just until they seem to hold on their own. You don't want to press them all the way in because you don't want them to show on the inside of your pot. Take any extra hypertufa mix and wrap them around the legs to further secure them into the pot. Make sure the mix is touching each side of the spike to ensure a strong bond between the metal and the mixture. If you have trouble getting it to stick, misting the mixture with a little water should help. Eyeball the legs to see if they are level, or use the plywood and level tip as described above.
Cover the project with plastic and mist the project every few hours with water if temperatures are above 80 degrees.
Step 9 - Unmolding
After 24 hours, it is safe to remove the planter from the mold so that you can sand down the rough edges, but do not but any weight on the legs as they are not strong enough to hold the weight of the still damp pot. Using the metal file, rub the edges of the pot, smoothing them down to your liking. If you forgot to make your drainage hole, you can drill one out with an electric drill at this stage. Mist the pot, inside and out then place it back on top of the sand mound to dry another couple of days. Cover with plastic and continue to mist with water a few times each day.
After about a week, take the pot off the mound of sand and continue to allow it to cure for a full 30 days before planting. Allow the planter to get rained on or soak the planter in water for several days to remove any lime that is in the Portland Cement before you plant it.