While I'm new and still learning, I'm using 8"x10" flat canvas panels. I have been trying different brands.
Here is one from Amazon that seems to work the best so far: https://a.co/d/1D3E5Mb Artlicious Canvases for Painting - Pack of 24, 8 x 10 Inch Blank White Canvas Boards - 100% Cotton Art Panels for Oil, Acrylic & Watercolor Paint.
I've ordered these several times and the product has been consistent and no boards were curved or warped.
The other brands I have tried are Gotideal, Esrich and a brand from Michael's. Esrich works well too.
08/21/2023
I recently ordered panels from Arteza. These are much thicker boards and heavier than the other brands I've tried. These are a bit more expensive but I'm confident they will work well with my vision.
