If you have an older Garmin watch that is not compatible with the Stryd Workout app (i.e the watch does no support CIQ 3.0 or newer), you could use Garmin Connect to create structured workouts yourself (but not power-based).

When executing this workout, the Stryd Zones data field will not show the correct average lap power as the demarcation of the segment is not forwarded to Stryd Zones. You can still get the correct average power for the segment if you use the lap button on your watch when the watch switches to the next segment of your training.