You don't need a base to do that. You need a platform that is higher than a zed can jump, and enough walls that they can't knock it over during BM. Thankfully there are hundreds of such platforms in every map.
How little does basebuilding matter? Below is my crafting base. It is outside next to the trader. This is because there is no reason to hide a crafting base. Nothing ever attacks the crafting stations. Witches just bring me XP pinatas. In MP this might not be viable.
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This is a fun base I am building for fun. I don't know if I will ever use it to BM. I will undoubtedly give it a shot when (if) it is done. Gathering resources for concrete takes so long, I have no idea if it will be. Probably not. I suppose it depends on if the next patch breaks saves.
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My BM base is a simple 2-story house that has lasted with very minimal repair. I will not be repairing it for this BM because it is kaput. I will probably just use the house next door to make a simple shooting platform, and wait for dumb zombies to stream in so I can execute them. There is no reason to waste all the effort I spent gathering thousands of stone, just for zombies to knock down my for-fun base.