I do something similar but the zip bags will work the same way! Early spring when the soil is cold and germination takes over a week or more I put lettuce in a box or bucket of soil in the house. After 3 to 4 days I simply pour the soil in a outside row and it has already sprouted!
You can do that with almost any seed. Peas work greatthat way!The advantage is also the dirt or potting mix has no weeds and the seeds start nice without any weeds in the row till they get going on their own! I do this in a cold frame also by pour the stated seeds in the cold frame then add another amount on top the seed started mix! If you can gain ywo weeks on the season that makes a difference especially with Brussle Sprouts or onion seeds! I like the zip bag idea and may use it for seeds thatI may only have a dozen to plant! Planting a sprouted seed and seeing the plant emerge the next day is exciting!
I enjoy fishing ,gardening and a solar greenhouse! carpet installation repair and sales for over 45 years! I am the inventor of the Bobber With A Brain - Fishing Bobber!