You can get little plastic clips that hook onto your J-tube to control the level it sits at in the carboy and keep it off the bottom. Or else you can improvise by using a clothes pin or by sticking a spare bung or cork into the carboy neck wedging the J-tube into position at the level you want it... then you'll have both hands free to start your siphon and get the business end of the racking hose into the new carboy, bottle, etc.