At one point in the Deep Jungle story line in Kingdom Hearts 1.5 Final Mix, you're sent to rescue Jane who has been kidnapped. While you're here, power wilds will continuously spawn around the arena, as long as the Black Fruit is not destroyed. You can take advantage of this to do some early game power leveling with Sora, Donald, and Goofy. You can also obtain all the required Power Shards needed for synthesis while you are here as Power Wilds drop them. You'll need about 20 in total.

Another option is to switch Donald for Tarzan, be sure to equip both of Tarzan's Critical Boost abilities to maximize his damage. Take your time and gather the Power Shards you need, afterward you should have gained enough levels that you can place Sora on a vine connected to the tall tree in the middle of the area and leave Goofy and Tarzan to do all the fighting.

Using this method it's possible to AFK farm a significant number of levels. The risk that Sora is knocked out decreases with every level gained. So make sure you take the time to gain a few levels manually first.

Be aware that if you are knocked out, then the progress you made since you last saved will be lost. Because of this I HIGHLY recommend leaving every now and then to save back at Camp. Just use the hole you came up from to get out again.

i am not the original finder im sure there are many that have found this years ago, games been around sense 2002. i found this by chance *then* found a guide on YouTube to confirm the method. i will provide the source here https://youtu.be/QBApAe7RLCQ they should take some of the credit for the better information i copied to post here to help anyone.