do not use rubber bands or twisties they will decompose, but you can use zip ties, epoxy, even drill and pin, but in general unless your building an unstable shape, stacking well is the best option. it takes some playing.....but that is half the fun......twist, turn and rotate till they fit securly on their own and they will not fall. and since this is your first post i'm assumming that you have at least a month of cycle time to play till your happy with your design........welcome btw