Put the chopped almonds in a dry skillet over low to medium heat, stirring constantly. Once the almonds become fragrant and aromatic, take them off the heat.
Add the overproof Rum and toasted almonds to the mason jar. Let this mix sit and infuse at room temperature for 24 hours.
The next day, open the jar and add lime zest, grapefruit zest, diced ginger, allspice, and cloves. Reseal it and let the mix infuse for another 24 hours.
After another day, strain the mix your homemade Falernum with the help of cheesecloth and a funnel into a bowl.
Thoroughly clean the mason jar and pour back the strained Falernum. Add fresh lime juice, almond extract, and cane syrup. Stir or shake to combine all ingredients before using your DIY Falernum in cocktails.