Cold tier in self managed cluster

can someone please help me understand this: Data tiers | Elasticsearch Guide [8.17] | Elastic

It says:
1/ cold tier uses searchable snapshots
2/ it can also be used with a replica

How do I implement this in self managed cluster? I can reserve a HDD storage for cold tier. But without replica how do I ensure there is no data loss. What could I do so data is read from searchable snapshots?

Please advise