You don't need wind to create a slab but it helps. Think of it as an accellerator, like pouring petrol on a fire. Even without fresh snow wind can create new slabs in a few hours. All you need is a weak layer somewhere not too deep in the snowpack.
With the early season conditions. Thin snowpack we've got areas of weak hoar crystals forming. It is not as critical as last season but the conditions are dangerous in the Pyrenees and Southern Alps at the moment. We've had reports of skier triggered avalanches in these ranges including an injury at Bareges. This video is from the summit of Fubillons on the Spanish side of the Pyrenees. A dillema for the skiers, the only skiable snow is that which has been blown into the bowl in front of them. Th skier gets a cheap lesson in slab formation at the start of the season.