Philadelphia had the ball at its 25 with 1:28 remaining and no timeouts left. Wentz, who did not turn the ball over in his first three games, heaved a pass to Nelson Agholor on first down and Slay made the game-sealing interception at the Detroit 23.
The Lions scored on all three of their drives in the first half, building a 21-7 lead late in the second quarter.
The Lions gained just 19 yards on the first four possessions, fumbling once and punting three times.
Philadelphia, meanwhile, opened the second half with Wentz capping a nine-play, 75-yard drive with a 1-yard TD pass to Josh Huff.
Copyright 2016 by The Associated Press