So Facebook is rolling out another functionality change when nobody was watching. If you are an administrator on a page, you sometimes want to like a post as yourself, not the page. To do this on the desktop, click on the drop down at the bottom of the post.
The next display will depend whether the change has been rolled out to your page. On some newer pages I manage, we see the following screen
Clicking the back arrow at the top left (circled), show you
You can then select to post or comment as yourself or another page.
On older pages, you will not see the middle screen.
Note: you can’t post as yourself using either the Facebook or Pages app (at the moment!)