I sleep trained my first daughter around that age. Put her in the cot so she wouldn’t come out, and could only move around within it. At that point, no other method worked anymore, so we did the cry it out method, and within 2 weeks, she was able to not cry and go to sleep on her own after we put her in the cot. So for my second child, we trained her since 4.5 months 😅 before she can sit/walk