Add the frozen berries and juice from a lemon to a saucepan
Simmer over medium heat stirring occasionally until the berries are thawed and juicy (about 5-7 minutes)
Once the berries are juicy, add chia seeds and continue to simmer for 5-7 more minutes using a fork or spoon to help mash to your desired consistency as needed
Turn off the heat and let the pot sit to thicken for 5-10 minutes