Looking for some recommendations for riding in the chamonix valley, can travel a little bit, hoping to get about 3 days on the bike.

fast flowing singletrack is my kind of riding, not so much into the freeride or massive jumps,

cheers in advance

No help for Chamonix sorry but if you like fast fairly technical riding take a look at Pila to Aosta just through the tunnel… or Samoens (about 1h away also).

There’s a cycle path/footpath heading up the valley along the course of the river. That has some nice bits if you explore around there. Eventually (2h) you arrive at the chair lift at Le Tour – take it to the top (money well spent), then there’s some cracking stuff on the other side of the big hill there.

I’ve probably got a strava thing somewhere with the route on it.

(The marked runs that go down next to the lift I found somewhat underwhelming).

“The Blair switchback project” looks entertaining, maybe next year!.

Don’t forget peak season bike ban on the walkers trails.

Are you in Chamonix the now or is it after August?
Either way, for fast n flowy singletrack you’re best looking up at Le Tour, as oldnpastit says, the trails from the Col du Balme above the Le Tour lifts heading for Trient, Chatelard and Vallorcine are all great and fit the bill. The Vallorcine gondola closes at the end of the month though. If you take the train or bike bus up to Le Tour/Montroc and buy the 31euro all area vtt pass then you can do a lap or 2 at Grand Montets on the way home too. The Lavancher trail is the official trail down from the gondola, but you’ll get away with riding the fast n flowing (fast n flowing is relative to ability) switchbacks down to Chosalet, though it is technically part of the bike ban.
Down at Les Houches it’s a bit rootier and less flowy, but there’s still great trails there. I’d just get the 21euro vtt ticket there and ride the Prarion and Bellevue lifts. There are some amazing options down to Le Fayet/St Gervais from there which can either involve the train (10 euros maybe) or the Tramway du Mont Blanc to get back.
The nearby Portes du Mont Blanc is great value at 17.50 for Megeve, St Gervais and Les Contamines.
The standard recommendations still stand though. Buy the Chamonix Bike Book from Tom in ZeroG, check out the Chamonix bike blog (here’s one on the bike ban http://www.chamonixbikeblog.com/2017/unintended-consequenceschamonix-bike-ban/ ) or just hire a guide (Wayne is awesome) http://www.chamonixmtb.com/

Second recommendation for Wayne. He knows the place inside out!