Flow to set alarm wake-up time based on time going to bed and add 8 hours

Hi all,
Hopefully you can help me.

When I go to bed I manually start a flow that says I’m asleep and after that other flows makes sure that lights, devices go out and logics are set.

I would like to create a flow that does the following.
When I go to bed register the time ie. 22:00 add 8 hours and set my alarm to 6:00

This way when I go to bed a little earlier or later my alarm will auto adjust to my preferred 8 hours of sleep.

I was hoping this could be done by usign logic and the option to set alarm but I haven’t found a solution yet.

So you have any ideas?

When this flow is started

Then start countdown timer AlarmTimer of 28800s

When countdown timer AlarmTimer reached 0

Then do the things you want to wake you up

I also had this idea but assumed that the Countdown timer app would have issues with such large numbers. Tested it last night and this works perfectly!
Thanks @peltsi51