The mix for soil blocks is a lot like muffin mix. It needs to be just wet enough to hold together. don't over work it or over water it.
Putting blocks in the tray. The air space between the blocks keeps the plants from growing into another block or from getting root-bound.
A full tray ready to plant. The little dimple in the top is for the seed. Cover the seed with a bit of fine compost if needed. There is also an attachment that changes the dimple into a cube the size of a mini-block. Makes transplanting easy.
The blocks hold together quite well. There is always a corner in the flat needing one block. If they are made right you can just pick one up and fill the hole.
Another favorite tool. I use landscape rakes on my raised beds to do the fine prep before seeding. Some short lengths of pvc pipe make great row markers, and you can easily change the spacing. This is for a block of salad mix.