Icon Maker can be used to quickly and easily create 32-bit color icons from images that already contain alpha information.
Extract all files from the zip and run IconMaker.exe. .NET 6 is required.
Drag images of equal width and height into the window. Select Save from the menu to create a .ico file containing the images. For best results, make sure to use an image format that supports alpha information such as .png.
All sizes from 16x16 to 256x256 PNG icons are supported. Icon Maker only supports writing 32-bit icons; any format image may be imported, but icons will always be saved in 32-bit color with an alpha channel.