The Hexblade warlock's Accursed Specter feature (XGtE, p. 56) says:
When you slay a humanoid, you can cause its spirit to rise from its corpse as a specter [...] It obeys your verbal commands
Does commanding the specter require my action?
The Hexblade warlock's Accursed Specter feature (XGtE, p. 56) says:
When you slay a humanoid, you can cause its spirit to rise from its corpse as a specter [...] It obeys your verbal commands
Does commanding the specter require my action?
In the Basic Rules Combat section it says:
Other Activity on Your Turn Your turn can include a variety of flourishes that require neither your action nor your move.
You can communicate however you are able, through brief utterances and gestures, as you take your turn.
A verbal command is communication, and can be performed on your turn without using an action so long as it is brief.
If it is complex or difficult to convey your command, then your DM may require you to take an action at their discretion.