Launching is the most critical time for slope soaring especially if the wind is strong. The slightest error in aileron trim will result in a quick crash. If you turn your back to the slope and hold the glider as shown in the photo, you will soon realise if the ailerons are not in trim, as the plane will tip either to the left or to the right very powerfully. You can trim the ailerons till the plane, stays level. Now is the time to launch it.