This is my current full stall 5th gen team. Nearly all modern stall teams incorporate a forretress so I decided to build a team without one.-0 It has done okay on the PO ladder so far.

Groudon @ Leftovers
Trait: Drought
EVs: 252 HP / 4 Atk / 252 Def
Careful Nature (+SDef, -SAtk)
- Stealth Rock
- Roar
- Earthquake
- Stone Edge

This is my lead to set up stealth rocks and to bring in the sun which helps against kyogre. Earthquake features as a nice and powerful stab to deal good damage to many things while fire punch is great as a lead as it prevents pesky forry leads from getting 2 layers. Dragon tail allows groudon to phaze some sweepers and it does not get affected by taunt while dealing adequate damage to dragons. I am considering stone edge to deal with ho-oh as it can be very troublesome. However, I find that fire punch is needed to take down forretress which is even more troublesome as a lead.

Arceus-Ghost @ Spooky Plate
Trait: Multitype
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Judgment
- Recover
- Flamethrower
- Roar

This is my spinblocker. With an awesome movepool, it can easily block a rapid spin and counter forry with flamethrower. Judgement makes an extremely powerful STAB move to take down physically defensive pokemon like groudon. Roar is a great phazing move that helps to deal with set up sweepers which can be a real problem to my team. Recover also allows for great survivability and a direct recovering move and it can attack while have great staying power.

Tentacruel (M) @ Leftovers
Trait: Rain Dish
EVs: 252 HP / 252 SDef / 4 Spd
Calm Nature (+SDef, -Atk)
- Ice Beam
- Toxic Spikes
- Rapid Spin
- Knock Off

I'm trying to build a stall team without forretress so I am using tentacruel and skarmory instead. One of tentacruel's primary advantages are that it can absorb toxic spikes and that it can take a better hit from some more powerful special sweepers. It can set up 2 layers of toxic spikes with ease. Ice beam can take down rayquaza and garchomp while knock off can just fill in as a crippling move to remove a foe's item when the job is done. The lack of ability to set up any other entry hazards really harm tenta's usage after the two spikes means that it cannot do as much as forretress but its greater special bulky, t spikes absorbability and a resistance to water and fire really helps.

Blissey (F) @ Leftovers
Trait: Natural Cure
EVs: 252 Def / 252 SDef / 4 Spd
Calm Nature (+SDef, -Atk)
- Heal Bell
- Wish
- Protect
- Toxic

There is no stall team without blissey. With its immense special bulk, it can take special hit bar specs kyogre's water spout and specs reshiram's blue flame. The heal bell is also very useful as it can stop my team from dying of poison, from reshiram burned and from darkrai ruining my team. With wish's new effect, I just can't not have wish and protect provides self recovery. I chose toxic over seismic toss because it can take down levitators and flying types (lugia cough cough). Btw, do not mention chansey as an alternative. I know it is bulkier but it dies easier to cuz there is no lefties, which I find really useful for self healing.

Skarmory (M) @ Leftovers
Trait: Sturdy
EVs: 252 HP / 4 Def / 252 SDef
Impish Nature (+Def, -SAtk)
- Spikes
- Roost
- Whirlwind
- Toxic

Skarmory is my best way of dealing with these hard physical sweepers. It is arguably the best counter to SD arceus, it can phaze and set up spikes. While it is not as great a phazer as lugia, the ability to beat SD arceus is very valued. Roost allows skarm to be very sturdy by recovering HP so it can continue to set up spikes and phaze. I chose toxic in the last slot as it can cripple a levitator or flying type and I can just wear it down. I am also considering taunt and brave bird, which would be able to deal damage to arceus.

Zekuromu @ Choice Scarf
Trait: TeraVoltage
EVs: 4 HP / 252 Atk / 252 Spd
Naive Nature (+Spd, -SDef)
- Outrage
- Lightning Strike
- Draco Meteor
- Dragon Claw

No matter what I do, kyogre is going to be the bane of this team. Because I have had problems with mono attacking CM kyogre, I am using reshiram to check it. It can not risk switching in to an unknown kyogre, but at least it can't sweep my team. It is also my revenge killer and cleaner to many sweepers and wallbreakers such as rayquaza, some arceus, some reshiram some mewtwo and some palkia. Unreliable, but it is the best way to deal with the faster threats as well as kyogre.

Some Threats (More coming soon)

Kyogre - Zekrom is frail and against specs ogre, I have no safe switch in. If I choose to use palkia instead of zekrom, Mono attacking CM becomes a large threat.

Reshiram - Reshiram can also wallbreak my team as I struggle to have a reliable switch in and I have to rely on zekrom revenging it or phazing it with arceus and it can nitro charge.

Groudon - I struggle to KO groudon. Arceus is the best way. If it is paired with kyogre, I have trouble.

Mewtwo - Cm set could sweep if zekrom is down.

My team does have weaknesses to common pokemon but fortunately, they are manageable and not completely unchecked. I am considering changing zekrom to palkia.