To associate a route table to a subnet all you need to have is your route table id and the subnet id.
The command used for doing that is as follows:
C:\Users\priyj_kumar>aws ec2 associate-route-table --route-table-id rtb-05f48298823c9731d --subnet-id subnet-08f4ee13b627d22bb
This will give you an Association ID.
This way you can attach a route table to a subnet explicitly.