Focus: Reforming walls great for newer skaters
I learnt this from a coach at another league, I don't know where they got it from or if they came up with it but either way: here's to Toxic Blocksyndrome one of the Bomb Squad and Bourne Bombshells coaches.
Part 1 - Get people into groups of 5 with about 6 'spare skaters' placed around the track. Set the 'spare skaters' off skating at a slow pace, laterally cutting across the track. Send the groups of 5 people off while one of them is nominated jammer. As the walls move around the track they will come across the other 'spare skaters' whom they have to split to move around and then reform the other side of them, while maintaining close to their own wall without letting the jammer through.
Part 2 - After people have become comfortable instruct the 'spare skaters' to actively attack the walls for a period of 20 ft. Get the blockers used to ignoring the offence and remain focused on the jammer.
Remember to swap in your 'spare skaters'.