Havent seen the show but I will attempt to descibe what they could have said.
First it propably was not just cement/ concrete, but actually Hypertufa (look at the fequently ask questions for more info) . Mix peat, portland cement and perlite in equal parts add water to a consistency of raw hamburger, not too wet, not too dry.

Get a bag of play sand, make it wet and mound it as deep as you want the planter.( start small then build to big pots) Cover the sand with plastic, dry cleaner bag will work. ( Mix only when temps are above 50f)
Then start to mound up the mix around the base going up sides. Covering the entire mound. About 1 1/2 to 2" thick. Make a hole for drainage
Start with a small mound - practice.
When the mound is covered with the mix, then cover the damp mix with plastic ( garbage bag will work) Allow the pot to cure for several days, ( if it begins to dry, wet with a hose) After a several days remove the pot from the mound.
BTW this is probably obvious, it would be helpful to make the base flat so the pot will sit firmly on the ground.

Mike

Hope this helps-

Here is a link that might be useful: Garden Design Ideas

Thanks! That sounds exactly what I want!

P.S. love your blog!