Prepare your mold (bucket) by lining it with a plastic sheet and cooking spray
In a large container, mix together equal parts portland cement, peat moss, perlite and water (mix dry ingredients first)
Press the mixture into the mold firmly, keeping a consistent thickness as you form the walls (at least 2"). You can use a second smaller mold inside, or build the sides up by hand
Cover your mold in plastic and wait 24-48 hours for the mixture to harden
Once the planter is dry enough to stay together, release it from the mold and use a coarse wire brush to rough up the surface
Place the planter back under plastic, mist it with water to prevent cracking and let it cure for another 3-14 days, depending on your climate, planter size and mixture ratio