CSS/Tailwind: Content material field above background

Hello i am on the lookout for some css assist, i am making an attempt to recreate one thing much like the format right here

The location content material is held inside a field with a border, with some parts anchored to the outer fringe of the field.

I attempted merely to create a div with a border + margin however it does not obtain the specified have an effect on.

Any pointers can be a lot appreciated!

 <div>
    outer content material
    <div className="border-2 border-slate-700 m-10 aspect-[2/1]">
        <div>inside content material</div>
    </div>
</div>

pointers in uncooked css (not tailwind) additionally very welcomed!

Thanks prematurely