Canva Design
Open Canva and use the approved thumbnail template. File → Make a copy. Rename the copy to the video name (example: Ark Encounter).
Clean Canvas
Delete all content on the page until you have a clean white canvas.
Creating the Thumbnail
Open the exported 1080p video file. Screenshot a frame that works as the backdrop. Scrub the video until you find a strong visual, then build the thumbnail on that background in Canva.