Installing templates on ES startup

When using ECK to run up an Elasticsearch cluster, via a Helm chart, what's the best way to install templates into a new cluster (PUT /_template/...)?

Possibilities would appear to include:

(1) Put some curl commands in the container's lifecycle/postStart. But they might run before ES is up and running, resulting in the template installations failing?

(2) Use a Helm post-install hook. But then clients of ES might connect and start using ES before the templates have been installed, resulting in wrong indexing?

(3) Something I haven't spotted yet.

What do people do that works?