To create a minimalist background in LWC (Lightning Web Components), you can use the @wire service provided by the simple-concat package.

Here's an example:

<template>
  <div class="background" wire:style="{ backgroundColor: 'var(--primary-color)' }"></div>
</template>

<script>
import { wire } from '@wire/service';
import { concat, stream } from 'simple-concat';

export default {
  setup() {
    const background = wire(stream());

    return () => ({
      background,
    });
  },
};
</script>

In this example, we create a background variable using the wire function and pass it to the stream() method. We then use the wire:style directive to set the background color of the element based on the --primary-color CSS variable.

Note that you'll need to define the --primary-color CSS variable in your stylesheet for this to work.