Line a muffin tin with 9 paper liners or use a silicone muffin tin. Set aside.
Melt 3/4 cup of the chocolate. Add 1 teaspoon of coconut oil to the chocolate if desired (see notes). You can use the microwave or a double boiler on the stovetop. If using the microwave, stop and stir every 30 seconds to ensure it melts evenly and doesn't burn. It should be melted after around 1 minute and 30 seconds, but it can vary with each microwave.
Pour the chocolate evenly at the bottom of each cup. Using a spoon, push some of the melted chocolate to the sides of the paper liners, about halfway to the top of each cup. This will make the sides of the cups and will ensure that the jam doesn't pour to the sides. Place in the fridge on a flat surface and let chill for 5 minutes or until the chocolate firms up.
Once the chocolate is ready, fill each cup with about 2 tablespoons of chia jam. Don't overfill them. It should just reach the top of the chocolate on the sides of the cup.
Melt the remaining 1 cup of chocolate using the same method, with 1 teaspoon of coconut oil if desired. Top every cup with more melted chocolate. Sprinkle a small amount of flaky sea salt on each cup if desired. Place in the fridge and let chill for 10 minutes or until firm.
Store the cups in an airtight container in the fridge for up to 1 week.