This will depend on how you set the website up but first will be to launch a new instance under free tier - t2/t3 micro (t3 isn't free in every region). Follow the same configuration setup and copy the content over. You should be able do this by attaching the EBS volume from your original instance to your new instance.
Note there is a difference between small and micro so ensure the lower instance type can handle your load.
You can see which services are covered under free tier at https://aws.amazon.com/free/
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