The inset is a powerful tool used in hard-surface modeling to get the effect of a cutout in your object with a smaller version of that object "inset" into it. This video will cover how to achieve it.
Take a look at HardOps to expedite this process; it's a lot quicker than the manual way (I am not in any way affiliated with this add on, I just use it personally):
https://gumroad.com/l/hardops
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Also check out my full course on hard-surface modeling and how to get started with the workflow: https://gumroad.com/l/vOFiv
Biz inquiries - josh@blenderbros.com