The world is designed for right handed people. It mostly means that intuitive designs aren’t intuitive, and a lot of things are slightly more difficult or awkward. Most left handed people I know are used to it enough that adaptations are not particularly noticeable, but there’s still plenty of ways to make life a bit better for everyone.
For your standard rectangular table with seating on two sides, there’s only two “left handed seats”: if you’re facing the table, the leftmost seat on each side. If you’re looking into a booth, it will be the seat all the way against the wall on the left side, and the seat closest to you on the right side.
High quality Text Diagram:
R R R R R R R L
L L L R R R R R
You can sit multiple left handed people in a row, as long as the first one starts at one of the two left handed seats; just as long as you don’t stick any right handed people in between.
Doing this right, you don’t have a left arm bumping a right arm while eating. It might not sound like much, but bumping arms and elbows during eating gets annoying fast.
Doesn’t have to be a lot of work, but checking quickly if anyone cares, or simply not filling up those seats first can make life a fair bit easier. Most Lefties that care about it automatically migrate towards those seats, so simply not immediately occupying them will make it easy for everyone to do the seating dance in a way that everyone gets the seats they want.