The best way to do this is to book the outbound one way as one separate booking with no hold baggage and pay for that. That's one complete booking, once it's confirmed with its reference number, by e-mail from easyJet.
Then, having done that ,make a one way booking for the inbound flight, this time with hold baggage and pay for that, again confirmed with its booking reference.. You then have two separate bookings, each with its own booking reference..You can , assuming you comply with the strict rules about cabin baggage (only ONE piece and of the right size) print your boarding pass online for the outbound, before you go, and avoid checking in at the airport, simply presenting the boarding pass to security (and be sure to still have it when you board the plane! ).