This is an orthographic sketch of the soccer goal. The sides would be the part “Slanting Standard” (4476). The net would attach by going over the studs on the tops of the Slanting Standards and then having a 2x10 plate go on top of the net, securing it to the Slanting Standards. The other end of the net would go on top of a 1x6 plate that would be in between the bottoms of the Slanting Standards. Another 1x6 plate would go on top of that, securing the net down. It would be good if LEGO made a wider net, because with the 10x10 net they have now, the goal isn't proportional to a real soccer goal. The diagram isn’t perfectly accurate at the top of the slanting standards because I drew them having only one stud. Unfortunately the bottom is cut off a little, too.