I gently taught my boys to self-settle by the time they were around 7 months old. I'm not sure if it works for everyone, but it worked for us

Both boys (and now DD) were rocked to sleep in the early day - DS1 in his hammock and DS2 in my arms. For DS2 I started rocking him until he was almost asleep and would put him down in his cot. I watched him and if he started getting upset I would pat him until he fell asleep, if that didn't work I'd pick him up and rock him off to sleep and try again the next nap. Over time I rocked him less and less so he was less drowsy and was mainly falling asleep by himself. Eventually he could be put straight in his cot and he would put himself to sleep. This took a month or two to finally work. Along the way we had failure with some naps and success with others, but I kept at it and it eventually worked .

DS1 was a different story because he slept in a hammock. I would do pretty much the same thing though and would bounce him until he was drowsy, but not asleep until he eventually worked out how to put himself to sleep. Hilariously he worked out how to bounce himself off to sleep in his hammock

I will do the same with DD once she starts getting closer to 6 months of age. She sleeps in a hammock for her day naps too atm, but I think I'll put her in her cot when I try teach her to self-settle. Hopefully my trick works for her too .