What did y’all do to get y’all’s babies to go to sleep alone like self soothe?

I’ve always slept in the same room with my two babies my 6 month and 3 year old. I tried to lay them down alone today and failed horribly. They started crying as soon as I layed them down and I waited like a minute before going in and went back out and same thing. They were both traumatized 🤦🏻‍♀️ idk what else to do. They sleep together btw but in their own crib/bed