1, first of all, we need to prepare 9 wooden doors, a number of cubes (any material can be), 3 villagers (can be replaced by villager eggs) and 12 half-steps.

2, according to the style of the picture below, build a 6-frame high platform, if you feel inconvenient to get the villagers up, you can dig down 6 frames, the principle is the same. The size of the platform is 5*5 so big.

3, we came to the platform, the villagers out of the push to the very center, surrounded by squares, the top put a good half-steps, you can prevent the villagers out, but also to avoid zombies and other monsters to go in.

4, after we then put a circle of wooden doors around, we can put more rows of wooden doors, and then use the square to seal the top.

5, we build a circle of walls to protect the villagers underneath this platform, or we can dig into the ground, the space should be big enough, and insert torches to prevent the monsters from brushing out, the villagers will stay here and continue to reproduce when they breed out. The rest is just waiting for the villagers to reproduce more villagers.