It’s easy to add HTML Back Button Icon without additional fonts links, Just write &laquo for the Back button icon in HTML

for Just follow the simple line of code below.

<a href ="#"
class = "previous">&laquo;
Previous</a>

I hope you got the answer to your question.

or you can use another icon for a different type of style.

there are a lot of icons in online like bootstrap icons, flat icons, fontwasome etc.