Batting does not give enforcement instructions in the statement of the penalty, therefore it is governed by the Three-and-one principle (2-33, 10-2-2-c).
The basic spot on a free kick is the previous spot (10-2-2-d-4-a)
The status of the ball is still a kick since muffing a kick does not change it's status. (2-11-2)
The kicking team (Team A) is in possession of the ball until Team B gains possession (2-4-a-b-1).
So this is a foul governed by 3-and-1 that was committed by the team not in possession, which means it is enforced at the basic spot, the previous spot. (10-2-2-c-3)
The result after enforcement would be A K/O on the B-35.
Note: The result of the play itself is a touchback, since the status of the ball is still a kick and muffing a kick does not change the impetus, so Team A is responsible for the ball being in the endzone and the ball becomes dead out of bounds behind the goal line. 8-6-1-a, 8-7-2-a