Poke a couple of holes in the squash with a fork. Microwave it for three minutes to soften the skin slightly, which makes cutting the squash much easier (and safer!).
Remove the squash from the microwave. Use a large sharp knife to slice off the ends, then stand the squash on one flat end and cut it in half lengthwise. (See Note)
Scoop out the seeds and pulp and discard them.
Brush the flesh of each squash half with olive oil, then season with sea salt and pepper.
Place the squash halves cut side down on a rimmed baking sheet and roast them for 30 minutes, or until softened. This results in slightly al dente squash strings; you can roast for a bit longer if you have a larger squash or prefer yours softer.
Remove the roasted squash from the oven, and scrape the insides into long squash strings with a fork. Serve with your favorite pasta sauce, or use in a recipe.
The squash will be a bit hot after microwaving; I held mine with a dish towel while slicing, which also helped me grip it more easily.
How to Roast Spaghetti Squash from Mashup Mom: https://www.mashupmom.com/how-to-roast-spaghetti-squash/