So when building walls, what is the easiest way to make sure there is no holes?

I always had to look super carefully and sometimes I still make mistakes. Also, I see players immediately build houses against the walls when I attack their walls. And this seems to effectively block my aggression into their village with houses even at 0% build level, which to me doesn’t make sense in the real world. However I thought I did the same thing but the houses at 1% didn’t block the enemy at all and they just managed to walk straight into my village. Maybe I am not fast enough. Any tips to break this defense or use them effectively?