....prevent flippy hair

It’s all in the cut. Firstly you need to find a stylist you trust and with whom you can communicate. Layers, which are the trend right now for longer hair, encourage flip out. And, just because they’re fashionable doesn’t mean they’re right for your face or hair type. Keep hair one length, which weighs down the ends if you want it to remain dead-straight. If you like the looseness that layers add, then just have them around your face to soften the style. Finally, you could use product and an appliance to keep things in place: try heat styling product to protect your hair and follow-through with the straightening iron.