Like most Pokmon cards, the value of Slakoth depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Surging Sparks)
Over the years, new card types have been introduced that look quite a bit different than your standard Pokemon card
I think the reason the card didn't make it to print was it was too strong
So, if you want to use Bounsweet in the second fashion that I mentioned, I would recommend making your Grass type deck, quick or free on the retreat costs, or have a Grass type deck that has Pokemon doing damage to their own Pokemon, that way you could try and get Bounsweet in the active Pokemon spot for a turn or two and heal your own Pokemon
It will also retain any subtypes it may have, such as Forest or Island
2016 POKEMON XY EVOLUTIONS MEWTWO REVERSE HOLO FOIL RARE - 51/108