The first thing you will see is a witch hut at spawn. And if you are lucky, or really unlucky, the evil witch is already inside. These witch hut seeds are quite rare as witch loots are really lucrative but they sure does exist, and this is one of them. Furthermore, this seed is possibly one of the best ones if you are looking for one instantly at spawn.
All credit goes to Jcorem
You really just have to spawn to see the witch hut. It will be in front of you so you would be blind to miss it. Make sure that you are not playing on peaceful, because then, nothing will spawn. In fact, the harder the difficulty, the better chance of a witch to spawn. Sometimes the witch does not spawn, but walk away and return overnight, just in case you really want to meet the witch in person.
As the norm, the witch hut is a big swamp biome. Which Hut at spawn is close to another biome which consists mostly of forests and grassland.