Symfony 4 AdminLTE template not working properly - symfony

Question

I am trying to implement AdminLTE for the AdminCP of my website in Symfony 4. I performed these steps:
Ran composer require kevinpapst/adminlte-bundle ^2.0
Ran cp vendor/kevinpapst/adminlte-bundle/config/packages/admin_lte.yaml config/packages/
Added .addEntry('adminlte', './assets/js/adminlte.js') to webpack.config.js
Modified package.json so it looks like:
This
{
"devDependencies": {
"#fortawesome/fontawesome-free": "~5.1.1",
"#symfony/webpack-encore": "^0.27.0",
"admin-lte": "~2.4.8",
"bootstrap-sass": "^3.3.7",
"bootstrap-select": "^1.13.1",
"daterangepicker": "^3.0.3",
"icheck": "^1.0.2",
"jquery-slimscroll": "^1.3.8",
"bootstrap": "^4.3.1",
"core-js": "^3.0.0",
"jquery": "^3.4.1",
"node-sass": "^4.12.0",
"popper.js": "^1.15.0",
"sass-loader": "^7.0.1",
"webpack-notifier": "^1.6.0"
},
"license": "UNLICENSED",
"private": true,
"scripts": {
"dev-server": "encore dev-server",
"dev": "encore dev",
"watch": "encore dev --watch",
"build": "encore production --progress"
},
"dependencies": {
"startbootstrap-blog-home": "^4.2.1"
}
}
Ran yarn install.
Added assets/js/adminlte.js with require('../../vendor/kevinpapst/adminlte-bundle/Resources/assets/admin-lte');
Ran yarn encore dev
The problem now is, the layout doesn't render properly at all. Like, it has the right text from the layout but it doesn't show the layout properly (see the attached screen).
See the problem with the layout here
The template rendered in my controller function of the route contains only this:
{% extends 'admincp/base.html.twig' %}
The admincp/base.html.twig contains this:
{% extends '#AdminLTE/layout/default-layout.html.twig' %}
{% block stylesheets %}
<link rel="stylesheet" href="{{ asset('build/adminlte.css') }}">
{% endblock %}
{% block javascripts %}
<script src="{{ asset('build/adminlte.js') }}"></script>
{% endblock %}
It doesn't throw an error or anything but it doesn't work either. It requests and gets the CSS and JS correctly.
(in case more information is needed, kindly ask and I'll provide it).