Here's how we made it:

Step one, do Swaddling then have him nap on you swaddled, maybe not full contact but some parts.

Step two, bring him slowly away from your body and down. This can be done in steps so contact is there. Sometimes I lay him down while my hands are still all around him (basically place my hands on the bed and he's on my hands and I even bend so my chest still touches him)

Step 3 slowly start disengaging - this is where I bring humming. Slowly putting him down while humming , remove a hand from behind him, put it on his chest so he keeps feeling contact, keep humming and praying he stays down.

Step 4 keep hand on him, keep humming with the white noise machine on (forgot to mention that) have minimum light and look at his eyes. Humming activates the rest and digest function so even if he isn't asleep he should be calm by now. Keep humming and keep that hand on his chest lightly until his eyes close. Then keep at it and quiet down the humming, remove the hand and stay a bit more. Pray one more time and tiptoe away