We can create a Vault Lock as follows:

1. Go to the Glacier service in the console.
2. Select our vault.
3. Go to the Vault Lock tab.
4. Click Create Vault Lock policy.
5. Add the following policy statement:

{
     "Version":"2012-10-17",
     "Statement":[
      {
         "Sid": "deny-delete-if-archive-age-less-than-year",
         "Principal": "*",
         "Effect": "Deny",
         "Action": "glacier:DeleteArchive",
         "Resource": [
            "arn:aws:glacier:us-east-1:135301570106:vaults/mybackupvault"
         ],
         "Condition": {
             "NumericLessThan" : {
                  "glacier:ArchiveAgeInDays" : "365"
             }
         }
      }
   ]
}

Replace my account ID of 135301570106 and the vault name of mybackupvault with your account ID and vault name. We can also click on Add a permission and generate the policy statement. 

6. Click Initiate Vault Lock. We should see the message shown in the following screenshot: 

7. Copy the Lock ID and store it safely. Click Close. We should see our policy details with the Vault Lock status reading In progress:

8. After enough validation, and within 24 hours of initiating the Vault Lock process, click on Complete Vault Lock.

9. Enter the Lock ID and select the checkbox for I acknowledge that the Vault Lock is configured as desired and that completing the Vault Lock process is irreversible.
10. Click Complete Vault Lock. We should see the status of Vault Lock as Locked.