It is part of the Sunnah that when a man sits down, he should take off his sandals and place them at his side.
Sunan Abi Dawud Book 34, Hadith 119
← Previous Hadith The Messenger of Allah (ﷺ) as saying: When the thong (of a sandal) of one of you is cut off, he should not walk with one sandal till he repairs his thongs. He should not walk with one shoe, or eat with his left hand.

Sunan Abi Dawud Book 34, Hadith 118 Next Hadith → The Messenger of Allah (ﷺ) as saying: When one of you puts on sandals, he should put on his right one first, and when he takes them off, he should take off the left one first ; so that the right one should be the first to be put on and the last to be taken off.

Sunan Abi Dawud Book 34, Hadith 120