Well, some seeds seem to germinate best in light and others germinate better in darkness. So, a lot would depend on what herbs you’re growing. You might find the link below helpful in that regard. Even when light is required for germination, very little is usually needed. I would think that if that opaque box is outside (but out of direct sunlight) enough light would be available to the seeds.

What you need to keep an eye on is the condensation within that box. If you see water droplets forming on the underside of the lid, it’s too wet (seeds might rot). A little moister is good, but not large water droplets.

If outside, make sure the box does not get too hot (75 degrees F. should be about right). Also, during the germination period, remove the lid once in awhile and let some fresh air into the box. Once the seeds start to sprout, the lid should be completely removed.

Hope this is helpful,

Art