I fact-checked. Three of the novellas were published online before Throne of Glass was released. They were released in anticipation for Throne of Glass. Source here.

Assassin and the Pirate Lord was released January 2012.

Assassin and the Desert in March 2012.

Assassin and the Underworld in May 2012.

Assassin and the Empire in July 2012.

Throne of Glass was released August 2012.

Only Assassin and the Healer was FIRST released in March 2014, which was when Assassin's Blade was published in print, after Throne of Glass and Crown of Midnight were already out.

These are facts. But no one's telling you which order you should read/ enjoy it. :) (If you call the ending of Assassin and the Empire "enjoying")