Black Forest Labs Publishes a Hands-On LoRA Training Guide for FLUX 3 Image Klein

Black Forest Labs has published a step-by-step guide to training a style LoRA for FLUX 3 Image Klein, using a collection of vintage Halloween postcards as its example. The walkthrough covers data preparation, captions, training settings and checkpoint selection, giving developers a practical starting point for customizing the open-weights image model. The guide uses AI Toolkit and FLUX 3 Image Klein Base, the model's non-distilled checkpoint for fine-tuning and research.