Bourbon is made in four steps: mashing, fermenting, distilling, and aging. The mash recipe must consist of at least 51% corn. Malted barley and rye typically make up the rest. Fermentation is usually completed with distillers yeast and the pre-distillation starting alcohol by volume (ABV) is usually about 10%. Initial distillation proof must be no more than 160, or about 80% ABV to maintain flavor. Bourbon must be aged in new white oak barrels and cannot enter a barrel at more than 125 proof. Once aging is complete, it is bottled at no less than 80 proof (or 40% ABV). Additionally, it is not permissible to use color or flavor additives in bourbon.
How to make bourbon – https://www.clawhammersupply.com/blogs/moonshine-still-blog/how-to-make-bourbon
How to make bourbon mash – https://www.youtube.com/watch?v=xrBfd4IlehA
How to distill bourbon – https://www.youtube.com/watch?v=GzrUloeNObo