@matigo You use a form that supports the neck / position the newborn relative to the fabric so they have some support. Check out the "Ideal Positioning" photo here: https://babywearinginternational.org/what-is-babywearing/safety/
Specifically: https://babywearinginternational.org/wp-content/uploads/2014/12/MT-85x11-01.jpg
I'm a big fan of this style carrier: https://babywearinginternational.org/what-is-babywearing/babywearing-resources/mei-tai/
Here's a video of how to use it with a newborn (one-month-old here): https://www.youtube.com/watch