Add frozen berries or other frozen fruit to a pot, and cook over medium-high heat to a simmer (approximately 7 to 10 minutes), stirring it occasionally.
If using larger pieces of fruit or whole strawberries, use a potato masher to break down the fruit to your desired consistency. This will also help it cook faster. Skip this step if using frozen sliced strawberries and/or other types of berries.
Remove from heat and allow to sit for 10 minutes to cool slightly.
Stir in the maple syrup and chia seeds.
Transfer the jam to the storage container(s) of your choice. The jam will thicken as it cools.
Allow it to cool thoroughly before storing it in the freezer.