A common problem at potluck buffets (where each guest brings an element of the meal)is finding space to serve what everyone has brought, and arranging it in a convenient manner. If you are hosting or helping set up the buffet table, The Kitchn recommends using post-it notes to label spaces for items in advance.
That labelling approach ensures you'll assign room for each person:
Make things easy on yourself and on your guests: have a post-it note with their name or the name of their dish already on the buffet table. This way, no one has to finagle for space between the macaroni salad and the dinner rolls, or wonder if the host wants their dish in a particular spot on the table.
It might also make sense to ask everyone for a rough estimate of the size of the dish they are bringing, so you can appropriate space accordingly. The full post at Kitchn has some other neat ideas too, like arranging the mains first and the sides later, or setting up a separate space for drinks.
How to Set Up a Buffet Table in 5 Minutes [The Kitchn]