If you draw on paper and need to storyboard a film in 2.39:1 (Scope, anamorphic widescreen) format, this free PDF storyboard template with 24 frames per page is a good starter for thumbnail sketches.
This template has two DIN A4 horizontal sheets with twenty-four frames per page, in 2.39:1 aspect ratio, ready to use, awaiting your drawings.
You can print it out and start drawing on paper. Another way you can use this template: open it in Photoshop, choose crop to Art Box or Crop Box in Import PDF > Page options and draw your board on a new blank layer.
You can get an editable version of this template for Procreate here: https://storyboards.gumroad.com/l/Procreate-24-thumbnails-scope-A4.