Straight hair isn't a one-size-fits-all affair. Type 1B hair tends to have fuller strands with a slight bend at the ends, but no real curl. To give this type volume and texture, use dry texturising spray at the roots before styling with a flatiron.
Celebrity examples: Lucy Liu, Kendall Jenner, Freida Pinto
Product recommendations: Oribe Dry Texturizing Spray (£39), Herbal Essences Naked Volume Shampoo (£4)