Help with crotch of reversible Jon jon

I'm making a reversible Jon Jon for my son. It has been very simple, up until the sewing of the crotch. Basically, the crotch is the last thing it says to do besides the hem. I'm having a reallyyyy difficult time figuring it out. I think the pattern is saying I should sew the crotch, right sides together, in a circle while it is still inside out and after of sewn up all side seams. I cannot figure this out, because when I do that, it basically sews up one leg when I try to reverse it.  I know that probably doesn't make much sense but if anyone has any insight I'd greatly appreciate it! Thank you!!