The best approach here is probably to just let a helper carry the kite some distance away, while you let out the line. Then tell them to hold the kite up and let it fly out of their hand when the next gust comes through. If the helper is a kid then just be prepared for them to hold the thing upside down though! Yes, it's happened more than once to us. Not all kids know how to fly a kite.
Eventually, with some practice, you will be able to get good at hand launches. You dangle the kite from your hand, let the wind catch it and then let line slip through your fingers whenever you feel the kite pulling. If you do it right, the kite quickly gets higher.
Hand launching kites is a balance. Let line out too slow, and the kite is still low down when the wind dies. Let it out too quick, and the kite loses height, perhaps all the way to the ground! Climbing a kite is a process of letting out line when the tension is strong, and holding on when the tension is light.
I had plenty of practice hand-launching while developing a series of
kite designs which used bamboo BBQ skewers for spar material. For
example the 2-Skewer Barn Door featured in the photo further down...
When the weather's good and you have the time, it's great to get out with a kite or 3. But what about on bad weather days? Then it's time to pull out...
"Kites Up!" - my downloadable kite-flying board game! Apart from towing indoor kites, doing a spot of imaginary flying is the next best thing :-)
tip: Unless your spool or winder is designed to let out line
continuously, it is easier to just pull off a fair amount of line onto
the ground before attempting to get the kite flying. It's easy to slip
line through your fingers when you don't have to try and unwind it at
the same time!
When the tension is very light, you might
even have to give the kite a hand by pulling line back in! This can be a
lot of fun, when trying to keep a kite up in wind that is barely strong
enough to make it fly. I can recall several times when I have brought
the kite almost all the way back to my hand before managing to climb it
away again up to several hundred feet in the air. When you can do this well, you'll feel like an expert!
Whenever you need to lay line on the ground, try to move around a bit so it doesn't pile up in one spot. Knowing how to fly a kite includes avoiding nasty tangles!
MBK 2-Skewer Barn Door
MBK 2-Skewer Barn Door
As mentioned earlier, there's another alternative to towing indoor kites if it's just not possible to fly outdoors...
"Kites Up!" is my downloadable board game. It's a PDF file which has all the documentation for the game plus images for all the components. Tokens, cards, the board itself and so on. Anyway, just click that link to see more info :-)