I haven't tried it myself although I keep thinking someday I might.
I've seen video and detailed photo essays of how to do it, and it does not look at all difficult or complicated apart from you need to plan things so that whatever drainage holes, level base, 'feet', etc you are going to want will end up the way you want them.
My husband loves working with concrete and we have a ton left over from remolding our septic tank (long story, lots of work and damage!).
I bet we could do this so easy. I was dying for some new pots around here... and those would look awesome stacked in my raised beds and out to give the illusion of tiny raised beds.
I showed this to my husband and he said "Lets do it!"
We looked at Home Depot last night. (He wanted to go look at the kits for the swing sets because he's planning on building one for our daughter, and with everything going on he's trying to make himself busy lately)
Now he's just going to 'supervise' me doing this... but that's huge that he thinks its a great idea to make some. I like it when he shows interest in my gardening.
One question though... we are not sure what Perlite is?