Fire Emblem Heroes: Squad Assault 10 Clear

Here's how I passed Squad Assault 10 to acquire the Squad Ace J Seal (Atk+1). There are F2P guides you can use for this, but I didn't have many of the necessary units.

You'll probably want to equip all the required Skills and Seals before you begin. Remember to write down which units you are going to use, along with any special requirements for each one.
  

*** Obligatory Possible Spoiler Warning ***

Chapter 6-3: Blunt Princess

Team:
1 - Sigurd 5*: Red Sword Tank
2 - Gunnthra 5*: Ranged Damage
3 - SM! Eirika 5*: Ranged Damage
4 - Olwen 5*: Ranged Damage

Notes:
Just an excuse to bust out my decked out Bladetome cavalry units. Archers or fliers also work.

   

Chapter 7-3: Baffling Labyrinth

Team:
1 - Lilina 5*: Red Mage (High Res)
2 - Leon 4*: Ranged Damage
3 - Azura 5*: Dancer
4 - Nino 5*: Ranged Damage (Nuke)

Notes:

Nino and a dancer are essential here. Lilina could be swapped for any ranged unit capable of destroying the enemy Nino. Leon is not really needed, any ranged attacker who can break a wall will do.

   

8-3: Ravishing Battle

Team:
1 - Fjorm 5*: Distant Counter Tank
2 - Lissa 4*: Healer
3 - B! Cordelia 5*: Archer
4 - A! Tiki 4*: Red Magic Damage

Notes:

Fjorm and a healer are essential here. A! Tiki is mainly for taking out the armored Axe Knight. B! Cordelia is mainly for Camilla in case she causes trouble.

   

9-3: The Blue Crow

Team:
1 - Olivia 4*: Dancer
2 - Xander 5*: Red Sword Tank
3 - Reinhardt 5*: Ranged Damage

4 - Cecilia 5*: Ranged Damage

Notes:

This map has a lot of annoying trees, which is bad news for cavalry units. However, I have heavily invested in my horses and was able to clear this map with three of my best cavalry units and a dancer. It would have been much easier if I had some good infantry mages I could use. The lesson here is: If you can't beat it, use The Reinhardt and friends.

   

10-3: The Imperial Prince

Team:
1 - Priscilla 5*: Healer
2 - Ryoma 5*: Red Sword Tank
3 - Camus 5*: Blue Lance

4 - Jeorge 5*: Ranged Damage

Notes:

Remember, this is a survival map, so running away until the time is up can work. A decent red tank is needed to take hits from the invincible Titania. A healer is also useful to keep your units alive. An archer can take down the two flying enemies with ease.