The loss was the Ravens' first in the preseason since Sept. 3, 2015, halting their NFL record at 24 consecutive exhibition-game victories.
Jake Fromm threw a 15-yard touchdown pass to Jaret Patterson with 4:08 to go as Washington (2-0) pulled within 28-26. The attempted two-point-conversion pass was incomplete.
The Commanders got the ball back with 2:54 remaining, and they drove 60 yards on 14 plays to set up Slye's winning kick. Slye ended the night 3-for-3 on field-goal attempts.
Washington's starting quarterback, Sam Howell, wound up 19 of 25 for 188 yards and two touchdowns while playing the entire first half. Jacoby Brissett went 7 of 11 for 47 yards with an interception, and Fromm hit on 10 of 16 passes for 91 yards and the one score.
Baltimore (1-1) sat out quarterbacks Lamar Jackson and Tyler Huntley, with the latter nursing a hamstring injury. Josh Johnson (10 of 12 for 145 yards) and Anthony Brown (6 of 10 for 40 yards) split the work under center, with each throwing two touchdown passes and an interception.
Ravens rookie tight end Travis Vokolek made two TD receptions.
—Field Level Media