If you can't make an outside pen you can create nesting areas inside with a bit of rearranging. .. our main coop is a 12x12 building, it has a 'man door' in the center, you step into an area nearly 3 ft deep which we call the 'people area'....it is used for storage and as a safe place to get into the coop without birds getting out. There is a chicken wire wall with 2 doors into the chicken area of the coop, normally it is one large space but we have removable chicken wire panels which can divide it in half if needed.
To the left and right of the people door we made a wide shelf at approximately 3 ft high, under these shelves are two broody areas. This allows the hens to have access to the people area floor to scratch, dust and stretch but they remain in the coop within sight and sound of the flock. We have used cat and dog crates to establish broody areas within the main coop itself if needed, sometimes the hens just remain in their chosen nest boxes with no separation, depends on what the hen needs. Most do move to the people area for a few days after hatch to let the chicks get mobile before joining the rest of the flock.
A few pictures....
Front of coop, to make more sense of above explanation
Pidgy with a couple of her newest chicks, she is sitting in the 2nd broody area which is to left of the door, we have a removable wire frame that secures in front of it if needed, she likes messing up her hay...lol
Dillon posing in front of the main broody hut, currently occupied by a grouchy buckeye!
This broody hut has a lift up front wall with a pop door so we can decide how much privacy is needed. I had it shut while I had all the other doors open while cleaning so she did not get raided by nosy hens.
With a bit of scap wood and chicken wire or hardware cloth you can make multiple frames which can be fitted together with zip ties to create barriers and establish broody areas within the coop. Make 3 or 4 ahead of time so they are ready to use when needed. It doesn't need to be fancy at all.