What is the best way to launch a glider?
FHHuber gave you all the options. I flew my first RC sailplane in 1949 when RC equipment was large and cumbersome with a severe weight penalty. Later went to a hi-start which will still work with enough space available. Lately I have been flying electrics because I live in the mountains and there are a lot of airplane eating trees. With the new light weight radios and electric gear it's a good way to launch. Geared motors and small high capacity batteries and speed controls you can climb back to altitude if you don't catch a thermal the first time.