I don't drink whiskey but do drink quite a bit of iced coffee and love that the large ice ball doesn't melt as fast as the normal size ice cubes. For this reason I started making them for my iced coffee and the silicone molds work as expected. They are easy to use and the ice is easily removed so I am very happy with my purchase.
https://www.amazon.com/Tker-Silicone-Whiskey-Cavity-Reusable/dp/B07FDBS4QC