I hate this valuable resource not being filled with proper examples; Lets change that!
With Frolass being our newcomer and quite a few metagame staples moving to PU, people might find themself overwhelmed by the new meta. I want to share some of the offensive and defensive cores I found really useful or look promising. I will provide spreads and sets for the pokemon (click on the sprites), but they may vary depending on when you read this and how the meta adapts/what becomes the most prominent sets.
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Losing Eldegoss really hurts fat Spikes teams but the addition of Froslass as a Spiker is phenomenal overall and thus I feel like we gained more than we lost for the archetype. Morpeko is the best offensive Rapid Spin user we have right now which also has the benefit of revengekilling non-Choice Scarf Jynx and discouraging the use of Psychic type moves. Removing hazards versus Taunt Froslass is almost impossible with the little hazard control we have which makes it a consistent Spikes setter. Many utility options, way to many to list them all, makes it tough to safely pivot into it. Morpeko also lures pokemon like Rhydon, Stunfisk and Tangela which a more offensive Froslass can threaten out.
+ 
After Spikes, Choice Band is probably the second set people will be using the most. While in ZU, Gen 8 gave Froslass two strong physical STAB attacks in Poltergeist and Triple Axel. Its STAB combination is highly threatening and not a lot will want to switch into it. Filler options like Trick and Spikes weaken incoming threats and sets up hazards in favorable matchups. Ice Shard can be used to pick of weakened faster threats like Choice Scarf Gourgeist, Rotom and Sawk. Note that Froslass is pretty weak so you'd need a lot of chip damage. Alcremie benefits from Froslass weakening Dark types that switch into Poltergeist, hopefully removing them so DoubleDance Alcremie can win in the end. When opting for Dazzling Gleam, Alcremie acts as a wonderful check to said Dark types and forms a nice defensive backbone for Froslass.
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(flying)
If you are tired of using my BirdSpam, I have a new Silvally-Flying core for you to try out! SubToxic Klinklang and Silvally-Flying share quite a few checks like Stunfisk, Coalossal and Rotom. The cores works after the basic formula of overwhelming the shared checks and trying to win with the one that has the better matchup. They also have decent type synergy in Klinklang checking Ice types like Jynx and Froslass to an extend and Silvally-Flying checking Fighting types like Sawk and Throh.
Also Klinklang just slaps at the moment.
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Is there something that screams Tuthur more than nascar Miltank + Alcremie? This core makes use of two of the best pokemon in the tier right now. Miltank being able to check common annoyances like Choice Band Thwackey and Alcremie being the best bulky wincon in the tier just makes this core really easy to use. Miltank also gives Alcremie the room to run Mystical Fire as coverage. The benefit of nascar Miltank with Rocky Helmet is that you can chip opposing pokemon as effective as possible allowing Alcremie to clean up a lot easier.
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Very punishing offensive core. They have great synergy in different aspects. Both can chip down Fire types, overwhelming them together and Thackey lures physdef walls like Altaria, Tangela and Shiinotic which Jynx can the abuse. Both sets can be different, SD Thwackey + CSpecs or double choiced can all work very effectively. Very simple concept but highly effective if executed properly.
Grassy Terrain also turns Galarian Stunfisk in something that Jynx beats.
+ 
A pretty standard physical breaker + physical cleaner core. Sawk also provides Knock Off support vs Tangela which would otherwise be painful to deal with for Lycanroc-Midnight - Knock Off support in general is really useful, removing potential Leftovers/Heavy-Duty Boots. With access to a strong Close Combat, together they can also form a semi-Fighting spam core. Decent type synergy at least in Lycanroc abusing the Flying types Sawk draws in.