A. Detach the block volume from the full instance. Create a new instance of the same shape with a larger boot volume and rsync the state of the boot volume between the instances. Attach the block volume to the new instance.

B. Create a new instance with a larger boot volume size as well a new block volume which is the same size or larger than the one attached to the full instance. rsync the state of the boot volume and the state of the block volume between the two instances.

C. Stop the instance that is full. Create a manual backup of the block storage before making changes.
Detach the block volume, create a new instance of the same shape with a larger custom boot volume and attach the block volume to the new instance. Configure the OS and any related application(s) to access the block volume under the same mount point as before.

D. Create a manual backup of the block storage instance. Create a custom image of the full instance.
Once that completes deploy the custom image to a new instance.