Start from the largest, squarest source you have
An SVG or a square PNG of at least 512 px gives the sharpest results. A non-square image is centred rather than cropped, and a raster under 512 px gets a warning with its actual size, because the 512 px Android icon would be an upscale.
- You can paste a screenshot or copied image directly with Ctrl/Cmd+V.
- Dropping an .ico uses its largest embedded image as the source.