Good Flairs start with good circles and good splits. One of the most common mistakes when starting flairs is to begin to pike the circles, this is especially true at the 1/4 circle.
One drill I use, and I'll try to get it in video form (along with the progressions I use for teaching mushroom circles) starts on floor mushroom. The gymnast swings a 1/4 circle stopping in a side support with their legs apart in a wide straddle, with their hips forward. Next they swing to a 1/2 circle shape, going through their 1/4 circle flair drill and stopping in a support with their hips up and legs apart in a wide straddle. Once confident with the this they swing to a 3/4 circle shape, going through the 1/4 and 1/2 flair drill shapes, and stopping in a side support with legs apart again in a wide straddle. Finally, I have them do a full flair on the floor mushroom. Once they show me good flair drills at each spot, and the full flair on a floor mushroom. I have them go up to the mushroom and do circle, circle, flair, circle.
Hope this helps a little bit.