The name "Toxic Stomp" comes from "Stompy", which the deck seems to take after, and the poison flavor of the -1/-1 counter cards from Amonkhet.
An ideal turn-1 play is going to be either Experiment One or Young Wolf.
With Young Wolf, you'd want to play "toxic." Simply, you would cast a 2-drop like Channeler Initiate or Exemplar of Strength and put the negative counters on Young Wolf, removing any positive counters on it and letting it return with Undying. Sense Young Wolf is a bottomless pit for negative counters, you'd do the same thing with Plague Belcher, Defiant Greatmaw, Crocodile of the Crossing, or any creatures hit with Collected Company.
With Experiment One, you'd want to play "stomp." This is a bit trickier, sense the best target for your negative counters is going to differ. Luckily, even if a creature like Exemplar of Strength has to put the counters on itself, It still enters as a 4/4 and will trigger evolve up to three times. Having to "bite the poison bullet" isn't game ending though. Experiment One, Channeler Initiate, and Exemplar of Strength all have ways of removing negative counters from themselves, although Experiment One isn't the best target for the ability.
Sense the deck is reliant on having and using creatures, Apostle's Blessing, Hapatra's Mark, and Heroic Intervention are runned in order to help insure that. Hapatra's Mark is also helpful with removing counters in a pinch and Heroic Intervention can be helpful against land destruction, which is a thing right now.
Other cards in the deck are Butcher Ghoul and Old-Growth Dryads. Butcher Ghoul is simply a worse Undying bottomless pit, although is also triggers Plague Belcher's last ability. Old-Growth Dryad is both a ok, turn-1 play, an evolve trigger, and even a target for negative counters sense it could potentially take two hits or just one hit and still be a chump blocker.
The sideboard is just kind of thrown together. Abrupt Decay is just general hate, though i honestly should probably only run green cards in sideboard.
