After the recent skill changes, some of Bastion's element field spell skill requirements have been lowered, making it easier to activate. Papa-Corn can take advantage of that, making it into a level 4 monster with 2,700 attack!
Firm as the EARTH Can be used after your Life Points are at 3000 or below. Play the Field Spell "Gaia Power."If there already is Field Spell on your side of the Field, rerturn it to your hand. This skill can only be used once per Duel.
Using Bastion's skill "Firm as the EARTH", Papa-Corn becomes 2,700 attack, which is higher than a lot of higher level monsters that requires tributes. Since the requirement to activate the skill becomes easier, you can use Cosmic Cyclone to easily get the skill up AND banish your opponent's spell/trap card, preventing them from being used in the graveyard. Though this deck relies on either you, or your opponent, from having a field spell. If neither player has one, then it can be difficult to recover.
Black Brachios Can be a good support monster since it also gets boosted from the field spell. It can be used to flip your opponent's set monster to face up defense position, or from attack position to defense. This is so that you can safely attack into them without getting destroyed.
Gigantic Cephalotus: Also a good support since it's an earth plant monster that can increase its attack further.
Botanical Girl: This is used to search Papa-Corn from the deck since he's the most important one that the deck is centered around, but it can be more useful if you have other plant monsters as options.
Cosmic Cyclone: Possibly the easiest and best card to use to get to 3,000 LP so you can activate Bastion's skill(s). You can activate this during the turn your opponent sets their spell/trap card to guarantee that they won't chain it.
Mirror Wall: Also an effective way to lower your LP, as well as providing some good defense. You can activate this card just to pay the LP cost so you can use your skill.
Enemy Controller: It's always good for some offensive, or defensive plays. In case your opponent summons a monster that you can't handle, you can take control of it so you can attack directly. Black Brachios can flip your opponent's set monster to face up defense, you can then switch it to attack position with enemy controller to deal some damage.
Powerful Rebirth: With only 3 copies of Papa-Corn, you can use this to revive it from the graveyard, or bring back Botanical Girl for some searches.