Excuse me, I would like to ask how to connect the two boxes together. And I want to know if the initial ozone box was not completely filled with ozone molecules，at this point,whether making the box extended, and then using water solvent will cause the entire large box to be filled with water or not.
Assuming you are building a 4 x 4 x 4 nm3 box with each layer being 4 x 4 x 2 nm:
gmx editconf -f ozone.gro -o ozone_upper.gro -box 4 4 4 -center 4 4 3
gmx editconf -f water.gro -o water_lower.gro -box 4 4 4 -center 4 4 1
gmx solvate -cp ozone_upper.gro -cs water_lower.gro