I started with acloud.guru AWS Certified Solutions Architect Associate course.
If you get the pro subscription, you get access to labs without having to create your own AWS accounts. I think it’s 50 bucks a month, but you may be able to find this on Udemy for cheaper.
AWS Well Architected Framework.
Plenty of YouTube vids on that as well.
Read as many of the AWS whitepapers as you can
Get some practice tests. I went with the practice test bundles below. They’re difficult and you will probably fail at first, but once it starts to click you’ll do better. I hammered away at them until I consistently scored in the high 80s and low 90s.
Jon Bonso’s practice exams: $15.00
Stephane Maarek’s practice exams: $12.00