I'm cheap and lazy when I start seeds out. I take a newspaper. Wet it. Open it up. Sprinkle the seeds in. Close it back up and stick it in the oven for a few days. The oven is off of course. After a couple of days I pick the strongest seedlings and plant them.
For planting in Gravel beds, big seeds are easy to simply plant right in the gravel and I've been having really good luck with stuff like broccoli, cabbage, kale, turnips, kohlrabi, and other related plants seeded or sprinkled right in the gravel.
The little seeds I often just sprinkle over the top but sometimes I'll make a little trench and put a layer of gravel over them. Both seem to have been working. I planted peas deeper but not as many have come up yet.
Some beds I have constant inflow and they drain by pump on float or siphon. Other beds are getting flooded for 9 minutes per hour or 9 minutes per half hour depending on if I have 3 or 6 beds on that valve.