Shuumatsu no Izetta’s OST

Track 01 -  A Dream of One Day
Episode 01 first scene/flashback, when young Finé and puppy followed the trail of magic before she woke up in present time.

Track 02 -  Izetta: The Last Witch
Basically the show’s main theme, plays during their airborne reunion (Episode 01)
When Finé gave her speech at the pie cafe (Episode 06)
When Izetta went stone-spam with the magic stone in the bunker (Episode 11)
Izetta vs Sophie’s finale where she drained all the magic from the leylines (Episode 12)

Track 14 - Encounter
Flashback when young Finé meets Izetta for the first time (Episode 02)

Track 05 - Chase
Second half of the flashback where they go around playing with each other (Episode 02)

Track 19 - Memories of That Day
When Izetta tells Bianca of the day when Finé defended her from the village (Episode 04)

Track 04 -  The Legend of the White Witch
When Finé and Izetta were talking in the secret witch chamber (Episode 04)
Part of it plays when Izetta and Finé were up in the tower (Episode 09)
When Izetta woke up in the bunker with Finé and Lotte at her bedside (Episode 10)

Track 11 - Feelings for the Princess
Yes, the OST that plays during the iconic mountain yuri scene. And yes, that is the title of that track. Don’t you just love this show? <3 (Episode 11)

Track 07 -  Finé: Love Theme
Final scene where we find out that Izetta lived and they’ll both live happily ever after with each other (Episode 12)
Yep, the track titled as the theme for Finé’s love. This show is just the best <3  
Also plays when Izetta slapped Finé when the latter was about to give up (Episode 11)
There’s also a piano solo of this track:
Track 30 - Finé: Love Theme ~piano solo~

Other not mentioned are soundtracks that playing during the battles or when there’s exposition stuff. Just to mention a few:
Track 03 - Sortie!
Track 16 - Commencement of the Counterattack
Track 18 - Izetta’s Secret
Track 21 - Set Me Free!
Track 22 - Sophie’s Magic
Track 25 - Battle Mode Irruption
Track 29 - The Final Battle

Also, pretty sure there are a couple that weren’t included in the OST like when Finé tackled Izetta onto the bed (Episode 07), when Finé touched foreheads with her and during the Lord Redford guy’s party (Episode 08)  

But it’s also possible I may have missed them so leave a reply if I did.