The seedlings are ejected by the plastic tray being pressed down onto raised solid lugs, which push all seedlings out of the tray a little way, at the same time, so that each can be moved to the next potting on container by lifting using their true leaves .
The second attachment illustrates the very good root system. and the ease with no disturbance to the roots when potting on.
The seed was sown, second week in August, direct into this module.
The trays are expensive to purchase, but can be used throughout the year, and are able to be cleaned in a dish washer , but all I do is pop in some Milton or bleach into a washing up basket and soak all the parts for a few minutes.
The tray comes with a plastic clear lid, used to cover the sown seeds, which can also be used as a dibber making 49 sowing
spaces at once. This tray also doubles as a water reservoir.
Each is capable of raising 49 seedlings, in a very compact space.
I would advise waiting for four true leaves in the case of viola/pansy to ensure compact root cone.
Other seeds might be different , but you can always check without doing much damage by pressing the cones out automatically from beneath , carefully , without touching the seedlings ,for a few mm, and checking roots by sight.
If not enough root growth ,then just tap the tray base down on a hard surface when the plugs of compost settle back into the tray again to grow
on some more until ready to be potted on .