Midwife suggested that following a feed I try put him down instantly and not allow him to fall asleep
That's two different things and I think you may be misunderstanding your midwife suggestions.
It's largely impossible not to feed a newbie to sleep. This is widely accepted and if you can't feed baby to sleep this suggests a feeding problem. All healthy babies will be feeding until asleep at this age.
That said, you can (should - if you're aiming for baby sleeping independantly) put baby down straight after the feed. At a week old that basically means:
- breastfeed to sleep
- when baby unlatches (asleep) lift floppy baby into your shoulder for a wind. This rouses slightly but baby probably will go back to sleep on in your shoulder while being winded
- put baby down to sleep.
That last bit sounds easy doesn't it? It is easy when you know how, but requires some subtle behaviours to get there.
Firstly, recreate baby being held by swaddling. Quite tightly around shoulders. I'd actually do this after feed, before winding. Wind baby whilst swaddled. The swaddle also reduces stimulation so baby doesn't notice being put down so easily.
So with baby asleep on your shoulder after winding, position yourself next to where you're putting baby to sleep. Bend at the waist so baby stays next to your torso, in your shoulder until you are horizontal just over the mattress.
Lower baby last few cm to the mattress but bent over close. Feeling your breath, hearing you remains important. As your body moves away from baby, place your hand across baby's chest. This is to replace the feeling of being close to you.
Wait, don't pull away. If baby squirms or is disturbed, try shushing. Try a dummy, they are amazing. Stay close though with your hand on baby's chest and face close to baby's face until all calm and asleep. If crying lift and go back to shoulder swaying and repeat. Then very slowly extract yourself once fully asleep.
At 4 days old this is not about putting baby down awake. Independant sleep is just about finding gentle ways to put baby down rather than holding baby for the duration of the nap. If that's what you want to do, of course.