I use this recipe but 1/2 it for a 3lbs bag of apples.
A simple Homemade Apple Butter recipe that you can make in the slow cooker or Instant Pot. Canning instructions included, or freeze to store.
Tastes of Lizzy T (www.tastesoflizzyt.com)
It’s the primary usage of my slow cooker 
I’m not sure of other techniques. But I love just tossing them in on a day I’m doing house or yard projects, stirring occasionally and really making the house smell great.
I love Apple Butter!! Apples were on sale for $2 a bag last week so I got extra and made apple butter out of a bag. I use a crock pot. 1 bag of apples peeled, cored, and rough chunked with some brown and white sugar, cinnamon, and touch of salt. Cook for 10 hours.