best way to add an admin portal following best practices

Hi all, i am wanting to add a admin portal to my application https://mixiecooking.com/ this portal would be used for adding blogs, updating privacy policy, terms of service, etc.
I am wondering what the best way to do this would be, some options i have thought about

adding the portal as
```
/admin
```
```
/admin
```
At
```
[userId]/admin
```
```
[userId]/admin
```
using a subdomain such as
```
admin.mixiecooking.com
```
```
admin.mixiecooking.com
```
however this requires a whole other application to be built and maintained

My setup is using a monorepo, project can be found here https://github.com/jacobsamo/Mixie

What would the best way to build this?

Mixie

Mixie is a community-driven recipe platform where home cooks and food enthusiasts can collaborate on unique and delicious recipes

GitHub

GitHub - jacobsamo/Mixie: Mixie is an open source, community-driven...

Mixie is an open source, community-driven recipe platform where home cooks and food enthusiasts can cook, create and collaborate on unique and delicious recipes. - jacobsamo/Mixie