not enough room OOB

[oc]

How do you apply the rule in gym without enough room OOB so you tell the defense that they will have to stay back 3 feet from the endline until after the ball is passed inbounds? Is the inbounder now allowed to step over the OOB line without a violation? Specifically in a gym where there is only about 18 inches OOB so it is possible for A1 to stay behind the line-but impossible to throw a baseball pass without stepping onto the court?