It's only multiple flows for different things ... so weaving a Gateway and then splitting your flows to weave air to lift something would be 2 flows.

Creating 100 Arrows of Fire could easily be only one flow. In any case he doesn't do all of this at once:

KOD
Vows

Earth, Air and Fire went into a weave Rand did not know, six of them at once. Except that as soon as he saw the spinning, he did know. Blossom of Fire. Six vertical red shafts appeared among the Trollocs, ten feet tall and thinner than Rand’s forearm. The nearest Trollocs would be hearing their shrill whine, but unless memories had been passed down from the War of the Shadow, they would not realize they were hearing death. Lews Therin spun the last thread of Air, and fire blossomed. With a roar that shook the manor house, each red shaft expanded in a heartbeat to a disc of flame thirty feet across. Horned heads and snouted heads flew into the air, and pinwheeling arms, booted legs and legs that ended in paws or hooves. Trollocs a hundred paces and more away from the explosions went down, and only some got up again. Even as he was spinning those webs. Lews Therin spun six others, Spirit touched with Fire, the weave for a gateway, but then he added touches of Earth, so, and so. The familiar silvery-blue vertical streaks appeared, spaced out not far from the manor house, ground Rand knew well, rotating into-not openings, but the misty back of a gateway, four paces by four. Rather than remaining open, they rotated shut again, opening and shutting continuously. And rather than remaining fixed, they sped toward the Trollocs. Gateways and yet not. Deathgates. As soon as the Deathgates began to move, Lews Therin knotted the webs, a loose knotting that would hold only for minutes before allowing the whole weave to dissipate, and began spinning again. More Deathgates, more Blossoms of Fire, rattling the walls of the house, blowing Trollocs apart, flinging them down. The first of the speeding Deathgates struck the Trollocs and carved through them. It was not just the slicing edge of the constantly opening and closing gateways. Where a Deathgate passed. there simply were no Trollocs remaining. My hands! the madman howled. My hands!

He's knotting weaves, and starting over ... no where does he hold more than 12 or so weaves at once. An amazing feat to be sure, and unlikely more than a handful of others could manage this.