There are multiple ways to set an alarm with Siri. You can set it by time with the command: “Wake me up at [time]” or “Set alarm for [time]."
Set an alarm by the hour, with the command: “Wake me up in [number] hours.”
You can change, delete and turn off alarms with a command. You can start anew with the command: “Delete all alarms.” Siri will confirm before doing so.