Simple nautically-themed carvings applied to a box turn it into a sea chest - in this case a treasure chest toy box for our grandson.
We begin at the bottom of the box with the rope moulding. The rope moulding has many other nautical applications is carved into an 'astragal' or half round profile; this one is quite small but the method is the same for any size of 'rope'. You'll see the corners need special consideration. I have seen the problem avoided in turned (or carved), circular or oval mirror frames.
For subscribing members, below is my working drawing & tool list for the rope moulding and other parts of the Sea Chest project.