If there are holes in the small pots, then just put the small pot on top of the bigger pot filled with soil. Works fine.
Then you can keep sowing in the small pot, throw in some cover crop seeds as well and keep topdressing in the big pot.
For example:
https://overgrow.com/t/no-till-stacked-pots-of-joy/74382
No need to ever transplant anything anyway.