monkeybird you can buy a specific potato pot device thingy if you really want like this or for a more thrifty approach just bung a few tubers in any decent sized container filled with compost. You can use an old bucket, tubb trugg, old compost bag anything really that has some drainage (tub trugg will need holes put in it). Don't fill it up to the brim with compost but allow for space to earth up the potatoes as they grow (i.e just chuck some extra compost over the top as they grow)
ummm....the RHS probably explain it better than me
btw if you have an unheated greenhouse you can put your container in there and have home grown potatoes for christmas.