If you use a tub that seals well there is no need for seal a meal,
Seal a meal isn't necessary with the substrateless method and is a good way to get too much humidity imo.
how can you have too much humidity? the perfect egg box is to keep the eggs dry and have 100% humidity. if you are getting condensation too early. this isn't a humidity problem but a difference in temp problem which will cause condensation.