In a small sauce pan, stir together the blueberries, lemon juice, lemon zest and maple syrup. Cover and bring to a low boil. Let simmer until the blueberries have softened and released a lot of liquid (about 8-10 minutes).
Use a fork to mash some of the berries, being careful to keep some whole.
Remove from heat and stir in the chia seeds. Cover and let sit for 15-20 minutes to allow the chia seeds to plump and thicken the jam.
Store in a mason jar or airtight glass container, and enjoy within a week or so.
Notes
Let the jam cool and thicken. Once you stir in the chia seeds, the mixture is going to look soupy. That's okay. Cover and let sit for 15-20 minutes. That's all the time it takes for the chia seeds to absorb the liquid and plump up to thicken the jam.
Don't mash all of the blueberries. To keep the jam a little bit chunky, be sure to leave some blueberries whole.
Want a thicker jam? Use more chia seeds, or cook down the blueberries a bit before adding the chia seeds.
Want a runnier jam? Use fewer chia seeds, or add a splash of water to the jam to thin it out.