Add extra space at the end of the existing hash table and leave the old keys in place.

Create a new table which is larger than the original table. Then bulk copy keys from one table to the other (i.e. if a key is in location X in the original table, it remains in position X in the new table).

Create a new table which is larger than the original table. Then individually reinsert each key from the old table into the new table (i.e. if a key is in location X in the original table, it may or may not be in position X in the new table).