So some of you wanted me to make a guide so I hope this will do.
Synergy Time
The Guide
Step 1: Choose a pokemon to center the team around how about a gliscor

Step 2: Determine a set you'd like to try out, we have a gliscor who can be played both defensively and offensively so how about we make a little unique set.

Gliscor @ Flying Gem
Nature Adamant
Ability Poison Heal
Evs 204 HP 252 Atk 52 Spd
Acrobatics
Ice Fang/U-Turn
Earthquake
Tailwind
Now this set is unique it takes the sand veil offensive gliscor and twists it as tailwind is not typically used in singles. However we sacrifice speed for a little bulk and tailwind will give gliscor the speed it lost. Now for those who dont know tailwind will double the speed of your team for three turns. Now we have acrobatics as the obvious powerful stab move and with max attacking investment it will do a lot of damage. Next we have ice fang to hit dragons such as dragonite or salamence so we dont have to waste the flying gem, however we can opt for u turn if we desire to scout or preserve gliscor simply by using this move on the last turn of tailwind. Earthquake is the final stab move that we'll use for jirachi and metagross. Now the evs are custom made so that gliscor will have just enough speed to outspeed scarf base 110's with a positive nature while the rest goes into to hit points so gliscor will have an easier time setting up a tailwind and finally poison heal to absorb toxic from walls such blissey and get its health back. However if your running a sand team we might want to run sand veil however you might miss the status absorber.
Step 3: Figure out your weaknesses. In this case gliscor is weak to ice and water.
Step 4: Figure out what pokemon use these types. In our case common ones include rotom-w latios mamoswine politoed vaporeon and gastrodon. Now if you notice most of these pokemon are special attackers bar mamoswine so the best bet is to go with a special sponge.
Step 5: Find a pokemon to fit the requirements you need. In this case we need a special wall and a pokemon to take on water and ice so why not give a slowking a try
Step 6: Determine the set.

Slowking @ Leftovers
Nature Calm
Ability Regenerator
Evs 252 HP 252 SDef 4 SAtk
Toxic
Scald
Slack Off
Grass Knot
Now slowking is what you might call a specially defensive behemoth as it can sponge a specs draco meteor from latios and live with about 33% remaining this will allow slowking to also sponge scalds ice beams and surfs from pokemon and then recover them off via slack off or switching out with regenerator. Scald will allow us a nice stab and to get some damage off upon whatever decides to take it and potentially burn the opponent with the 30% chance. Next off we have grass knot which may seem weird but it one of the few ways we can hit gastrodon with this core while toxic will allow slowking to cripple and ware down opponents pokemon to a point where gliscor can come in and wipe out the rest of the opponents team
Step 7: Look at the two you have and analyze their weaknesses combined. In this case we have nothing to really take grass ghost or dark attacks.
Step 8: So looking at our weaknesses we may want a dark type which can also resist grass so lets take a look we could try houndoom bisharp hydreigon honchkrow and shiftry. Out of these pokemon we want something that can come in on gengar a pokemon neither of our pokemon will appreciate so we can go sucker punch bisharp or honchkrow but hydreigon houndoom and shiftry are out. So lets try honchkrow
Step 9: Determine your set so we have a few sets to try scarf or life subroost honchkrow.

Honchkrow @ Life Orb
Ability Moxie
Nature Jolly
Evs 4 Def 252 Atk 252 Spd
Sucker Punch
Night Slash
Superpower
Brave Bird
Now with the release of black and white two the don of pokemon into a new rage as you can now run superpower with moxie a thing that will make ferrothorn and skarmory quiver in fear. Sucker punch allows me to hit gengar and dragons that have set up very hard with a stab life orb base 80 move. Night slash allows honchkrow to still have a stab when the pokemon are predicting a sucker punch. Brave bird allows honchkrow to abuse its second stab.
Things to Remember
1. Orginality vs Stupidity
You need to remember that while originality is good there is a point where sets wont work obviously a physical slowking will not work well at all.
2. Threats
Any core will not be able to take on every threat however this makes it up to you to find a pokemon that will counter this threat or threats.
3. Rest of the Team
While gliscor may not be the only pokemon focused on this team you want to make sure you have pokemon that work with the pokemon already given to you.
Thank You For Reading This Has Been The Guide To Building A Effective Core