[Vuejs]-Layout Issue of vue-select in Vue.js

You of course realize that no CSS is applied to the markup, so you need to apply some cuatom CSS.

Or, see the Vue Select docs
how to include their default CSS:

The component itself does not include any CSS. You’ll need to include it separately:

import 'vue-select/dist/vue-select.css';

Alternatively, you can import the scss for complete control of the component styles:

@import "vue-select/src/scss/vue-select.scss";