How to teach toddler to fall asleep on their own?

Our 21 month old still takes a bottle of milk before she goes to sleep. We want to quit that and teach her to go to sleep on her own

We have a routine at night so she knows it’s bedtime. Then we go into her room with sound machine on, and we sit in a rocking chair and give her her bottle of milk and rock her. When she finishes the bottle, we stand up and put her over our shoulder and rock her to sleep mostly for maybe 10 mins, then lay her down in her crib. She’s fully asleep sometimes by then, not always. All of a sudden she’s been waking up maybe half of the time when we lay her down and crying, but we just leave the room anyway since she knows it’s bedtime. The whining doesn’t last too long and she falls asleep

Once she falls asleep, she is a great sleeper. She will sleep through the night. So our problem just is figuring out how to teach her to go sleep on her own. She loves her milk before bed so I think that alone will be super rough