Warm 2 cups of water on the stovetop in a pot. (You don't want to bring it to a full simmer, just warm the water enough to properly dissolve the salt.)
Add the salt and stir. Once the salt has dissolved, remove the pot from the heat.
Add 2-4 cups of cold water to it to cool it down; if you want to speed up the cooling process, you can add a handful of ice to it. Make sure the water is cool before placing the chicken into it.
While waiting for the water to cool down, prepare your brining bag. Squeeze the citrus fruits juices into it, then put the remains of the fruit into the bag along with the fresh herbs, smashed garlic cloves, and peppercorns.
For support, prop the bag into a large mixing bowl and carefully pour the cooled brine into it.
Transfer the chicken into the brine using tongs, ensuring that the breasts are fully submerged. Push out as much air as you can from the bag and seal it well to prevent leaks.
Pop the bag into the fridge for at least 30 minutes, up to an hour. (You could leave it for up to 2 hours, but you don't want to over-brine the chicken or it will become too salty and the texture will degrade and become spongy. I find that 1 hour is the sweet spot.)
When the brining is done, carefully rinse the chicken breasts in the sink. Do this with low water pressure so that bacteria doesn’t splash and spread.
Transfer to a paper towel-lined plate and gently pat the breasts dry with paper towels, then proceed with your chicken recipe. You'll be thrilled with how tender, juicy, and flavorful your chicken is!