the chicks will not be able to navigate the ramp for a week or so. They need to stay up or on the ground... or be put up every night when the broody goes in so they don't get cold. Some hens don't like chicks and are to rough with them and kill them... I had one that was rough but she got used to them... the broodies protection instinct is strongest the first couple of weeks and she usually can protect them from the other hens, until they get used to them.
Also a dish with a big opening chicks can drown in the first few weeks.. marbles or stones help with that.