Stable Diffusion 3.5 Large does pretty well out of the box (similarly to what I noted for Schnell in another comment, just using “An illustration in ligne clair

Stable Diffusion 3.5 Large does pretty well out of the box (similarly to what I noted for Schnell in another comment, just using “An illustration in ligne claire style…” as the start of the prompt) without any custom fine tuning.