Good questions.How tall is the current opening to the nestbox?
Is this meant for standard sized chickens or for bantams?
I had hatchery quality Sussex, Orpington, and similar breeds when I first started my flock. I put them in a tractor with nests 12" x 12" x 12". I started with the opening into the nests as 8" tall but they scratched out the bedding so I had to raise the lip another 2" to keep the bedding in. They were able to get in and out without problems but those nests were close to the ground. They could pretty much just step into the nets from ground level. So can yours. Those openings were 8" wide.
In my main coop my nests were 16" x 16" x 16". Some were high enough that the chickens had to jump/fly to get in them. The lip was high enough that they could not scratch out the bedding and eggs and the openings were 8" wide. Those openings were 8" high. Those worked well.
Your nests are really low. You want the lip to be high enough so they do not scratch bedding and eggs out of the nests when they are rearranging the nest bedding. You do not want them to scratch bedding from the coop floor into the nests as that bedding could have poop in it. I don't know what size chickens you will have or how tall that opening is now.