With Filter Chrome's Premium feature you can block YouTube (or any App) on your device by following the steps below. 

Block the app

1. Open Filter Chrome
2. Tap on Block tab
3. Tap on App Blocker
4. Tap on checkbox beside YouTube

Block the website 

This will block access via Chrome and SPIN Safe Browser

1. Open Filter Chrome
2. Tap on Categories tab
3. Scroll down to the YouTube.com category and toggle on

Prevent changed with Prevent Removal feature

Prevent Removal is a Premium feature that adds improved protection against removal and tampering of Filter Chrome. It also locks in your settings for Categories, Blocked Domains and Blocked Apps. 

1. Open Filter Chrome and tap on  this will open our side drawer
2. Tap Prevent Removal
3. Choose your Accountability preference: Self Managed or Accountability Partner
4. Select the delay for your token
5. Tap Apply.