I purchased some manure seed pots from Territorial Seeds.
I wanted to see how they work, and if it would be easy to make some for next season. (1/2 half of me is Scot), I squeeze pennies. I think these are made from cattle muffins.
A bag of seed starter and 5 oz. paper cups works very well for me. The packaged plastic tray with that grow medium that swells when you put water in it, in each tiny pocket, was a total disaster - not a single seed sprouted in that last year.