SvelteKit: how do I do slug-based dynamic routing?

I am a newbie on Svelte and in coding in general. I'd prefer to learn SvelteKit (Svelte@Next) rather than sapper since that seems to be where Svelte is heading.

For my personal project, I need to support dynamic routing based on url slugs. How do I do that in SvelteKit? For example, if I have /blog directory and need to pull content based on its "id", how would I do that?

The part that I am having difficulty with is accessing the URL slug parameter.

Thanks in advance.