Grab an exacto knife. Sorry, scissors won’t really cut it (hahaha) for this craft. Seriously though an exacto knife makes it so easy. For a container that your kids will share do not remove too much of the carton. For two individual Mayflower ships you could attempt cutting the carton into two equal parts.
I added a some “wood planks” to make it a little more fun and Little B thinks I should go back and add the nails by using dots. I may leave that idea for him!