Heat a sous vide water bath to 185°F degrees.
Cut the butternut squash in half and use a spoon to scoop out all the seeds and stringy parts.
Cut it in quarters, then carefully cut away the skin from each quarter.
Cut the peeled squash in 1 ½ to 2" pieces.
Place the squash in a bowl with all the ingredients (except avocado oil) and toss to fully coat it.
Place the squash in a vacuum seal bag and seal (or a Ziplock bag if using the water displacement method).
Place in the water bath and cook for 60 minutes, being sure to weigh it down so it doesn't float.
Remove from the water bath, open the bag and pour the liquid in a bowl and set aside.
Heat a skillet over medium high heat and add the avocado oil.
Add the butternut squash and cook for 2-3 minutes on each side, checking frequently to ensure it is not burning.
The outside should be light to medium brown and caramelized.
Once caramelization of two sides have occurred (you'll flip the pieces once), add the reserved cooking liquid back in and cook it until all the liquid evaporates.
Remove and serve hot sprinkled with flaky sea salt.