The Gulp setup supports Sass Globbing which means within Sass, you can use * to import Sass partials:

my-component
dist
_scss-partials
sass Created with Sketch.
_partial-1.scss
sass Created with Sketch.
_partial-2.scss
sass Created with Sketch.
my-component.scss

@import "_scss-partials/**/*.scss";

If the sass file of your component gets too big this might be a good idea to split it up within the component. Read more about when and how to split up Sass inside a component.