Learn French: J'aime toutes les saisons.

Saisons (seasons) is a feminine plural noun. Because tout is an adjective here, it has to match the noun it describes. Therefore, we use the feminine plural form, toutes.

Do I pronounce the "s" at the end of toutes?

No. The "s" at the end of toutes is silent. You pronounce the "t" sound, making it sound exactly like the singular form toute.

Do we always need les after toutes? Could I just say "toutes saisons"?

Yes, you need the article here! When using forms of tout to mean "all" or "all the" with a specific noun, French requires a definite article (le, la, les). So, "all seasons" translates to "all the seasons" (toutes les saisons).

Since aimer means "to love," shouldn't this mean "I love all the seasons"?

It can mean "I like" or "I love." When referring to things or concepts (like seasons), aimer usually translates to "to like." If you wanted to strongly emphasize that you love the seasons, you would normally use J'adore toutes les saisons.