one way to make a good base is to surround your base with walls, except for 1-8 places leave a small gap. troops automatically go towards the gap, so group defences around the gaps. another strategy is to make a long skinny path, free or almost free of buildings, towards the town hall, or resources. by grouping defenses along the path, you make sure that troops just go along the path and get themselves killed. for an example, look at my base "traps"