The answer may depend on the data in your hashtable. For relatively simple data
Export-Clixml and Import-CliXml is the native and straightforward
PowerShell solution, see another answer.
And, if you want to store many hashtables effectively then look for some sort
of document store solutions. I recently found that LiteDB is very good for many
PowerShell scenarios. So I created https://github.com/nightroman/Ldbc, the PowerShell wrapper of LiteDB, batteries included.
Using this way, you may store and retrieve thousands of hashtables.
As the default PowerShell hash table (@{...}) is of type Object, Object it doesn't concern just a HashTable type but the question implies serializing of any (value) type to disk.