No flaps, full throttle then lean the mixture. On the Robin you have to do it the old fashioned way - slowly pull mixture back until the revs start to rise followed by a sharp drop. Push mixture back in to the point the revs started to rise, you are now at best fuel/air mixture for your altitude. Now adjust your attitude to obtain the best rate of climb, but you’ll be lucky to get more than 500 fpm at that height.