[BTW, there is no definitive word on how the Last Supper was arranged].  That's what you think.  Formal meals, like the Passover, followed the cultural customs of the times.  People 'reclined on couches' at the table.  They leaned on one arm and dipped into sauces at the table with the other arm.  And they faced each other.  That's how Jesus and Judas dipped a piece of food in the same bowl.  As such, the seating was in a horse-shoe shape---with an opening for the servers to bring in dishes and take them away.  When Jesus washed feet, he was on the outside of this configuration, where the feet were, and he went from one apostle to another.