My import statement:
import Stuff from './components/Stuff';
My directory is laid out with explr as the parent directory, the components directory is a direct subdirectory of the parent dir, and App.js, where the import statement is, is in the parent dir.
My 'Stuff.jsx':
import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
export default class Stuff extends React.Component {
  render () {
    return (
      <View style={styles.sidebar} />
    )
  }
}
const styles = StyleSheet.create({
  sidebar: {
    position: 'absolute',
    left: 0,
    top: 20,
    height: '100%',
    width: 200,
    backgroundColor: 'lightslategrey',
    display: 'flex',
    flexDirection: 'column'
  },
})