You cannot put the baby down without them waking up. That is not a technique problem.

You have tried every version of the put-down

Lowering them a centimetre at a time. Keeping a hand on their chest for a full minute after. Warming the mattress first. Waiting five more minutes, then ten more, until they are properly gone.

Sometimes it works. Most of the time their eyes open somewhere on the way down, and you are back on the sofa starting again.

None of the advice you have been given is about the put-down. That is the first clue.

Everyone has a suggestion. Nobody has an answer.

All of it offered kindly. All of it about the feed, or the wind, or what you are eating. Not one of them about the thirty seconds where it actually goes wrong.

She asked a room full of strangers for a rule, because the professional she saw would not give her one. Nobody answered.

Here is what is actually happening on the way down.

They wake because the thing that was working stopped

Think about what you were actually doing in the twenty minutes before the put-down.

You were holding them at an angle against your shoulder. Or you were patting them, in a rhythm, over and over.

That was not you soothing them. That was a condition they were in. A specific angle, or a specific repeating motion. And when you lower them into the cot, that condition ends in a single movement.

They are not waking up because you moved badly. They are waking up because the thing that was working was switched off.

Which changes the question completely. It is not how to lower them more smoothly, and it is not how long to wait. It is whether that condition can carry on existing after your hands leave.

And that depends entirely on which of the two you were doing.

Neither is a treatment and neither will make them a different baby. Most of this settles on its own with time, and anybody telling you otherwise is selling you something.

Written by a stranger, to a mother who was not asking for reassurance. It was the only useful thing in the entire thread.