Focus on possession vs. penetration decisions of the field players. First attacker penetrates if possible, possesses when penetration is not possible. Start the activity having the field player just try to keep it from the defender, not allowing them to play the ball back. Teach escape moves at this stage as well as sideways on shielding. Defenders must look to constantly recover goal side and in line of penetrating passes.
Defender bends knees, channels, feints to tackle, etc.
In the same box, play 2 v. 1 for possession. Play 2 v. 1 to targets, continuous flow. Support, width, angles etc. 3 v. 2 then 3 v. 3 in possession then penetration. Same as the 2 v. 2 stage.