You can prepare the basil or chia seed gel in advance if you'd like -- see note below.
1/4 cup basil, fresh, packed
1 Tablespoon basil seeds or chia seeds
1 1/2 cups lemon juice
Add everything into a large pitcher and stir.
The seeds will swell within about 30 minutes, so it's best to let this sit in the fridge while that happens. If you want to speed the process, mix the seeds with 1/2 cup water about 30 minutes prior to making the lemonade and then add the seed gel to the pitcher and proceed.
Basil seeds for beverages are available in many Asian markets. You can also order organic basil seed in bulk online and use them in drinks and to plant for fresh basil!