Attack through the wide areas and finish from crosses. Get the ball into a channel, deliver a quality cross on the move, and time runs to the near, middle and far post to score.
Mark a wide channel down each flank. A team must play into a channel and cross to score, and goals from a cross count double. Limit the winger to two or three touches in the channel to force a quick, quality delivery. Coach the timing and variety of the cross and the runs into the box. Rotate the wide players so everyone crosses.
Conditioning a small-sided game teaches by making the wrong option impossible, and that is both why it works and what it costs. Marking out wide channels and requiring the ball to travel through one before a goal counts will produce more crossing in fifteen minutes than an hour of instruction. It will also, left running too long, produce players who go wide because the rule says so rather than because the middle was blocked.
So use it deliberately and then take the condition off. The behaviour you actually want is a player recognising a congested centre and looking wide as a consequence. The conditioned game creates the repetitions, and the free game afterwards is where the decision gets attached to them.
Inside the game itself the coaching point that matters most is getting the ball wide early. A team that works it out to the flank only after the defence has already slid across finds a full-back and a covering centre-back waiting, and the cross goes nowhere. Early means before the defensive block has finished shifting.
Two things worth saying to players honestly. Crossing has a low success rate even at the top level, so a session built on crosses contains a great many that come to nothing, and that is normal rather than a sign the session is failing. And a cross is only ever as good as the runs attacking it, which is why asking for near post, middle and far post on every delivery matters more than the technique of the ball itself. An excellent cross into an empty six-yard box is a wasted attack.
Save it to your private drills, then change the animation, adjust positions, swap equipment, or drop it into a session block. Or start from a blank pitch and build your own.