Wait for the berries to ripen to the point where they are mushy.
Place the berries and 1 cup of water in a blender and blend, on low speed, for 10 seconds. Allow the crushed berry solution to settle for 15 minutes.
Remove any seeds that float to the surface of the solution.
Line a strainer with 4 to 5 layers of cheesecloth and place the strainer over a bowl.
Pour the berry solution over the strainer and allow it to drip into the bowl. This may take several hours, depending upon how many berries you are using.
Place the seeds that are left behind in the cheesecloth in a small bowl and cover them with hydrogen peroxide. Allow the seeds to soak overnight.
Place the seeds on a paper towel to dry completely. Place them in an airtight container and then in the freezer for 8 weeks.
Remove the seeds from the freezer and allow them to come to room temperature.
Fill a nursery flat with equal parts of coarse sand and potting soil. Water the mixture until it is moist and scatter the strawberry seeds across the top of it. Sprinkle a 1/-inch layer of sand over the seeds and squirt the sand with water.
Cover the flat with plastic wrap and place it in an area that remains between 65 and 75 degrees Fahrenheit and receives indirect sunlight. Remove the plastic wrap when the seeds sprout, which should occur within 6 weeks.