Different conclusion to the anarchy maybe? Eustace or William becomes king so Henry ii never forms the angevin empire and normandy and flanders remains with the english crown but aquitaine does not. Brittany falls into english orbit after the death of Bertha as it did otl and you get a northern france under english control and southern france very much not.
Then you just need england to hold onto what they have.
Near to what I thought:
William Adelin survives the White Ship and his marriage with Sybilla of Anjou preserves the peace with Anjou; he later turns out to be sterile/impotent.
With William as Duke of Normandy, William Clito son of Duke Robert gets less support from the Norman Barons and so no 2nd Rebellion.
When Charles the Good of Flanders is murdered and King Louis promotes William Clito, Thierry of Alsace gets to form a better alliance with Henry I Beauclerc by marrying Mathilda, since she's not needed for Anjou, and rather than being last man standing for Flanders gets to beat Clito decisively.
As Mathilda sprogs it's clear there's a problem with William or Sybilla before becoming clear it is William. However William denotes his succession through Mathilda's line.
Stephen of Blois is still an important figure in English Royal circles and he gets to marry his son Eustace to a daughter of Mathilda.
When Mathilda's son dies, Eustace gets picked as replacement and while there is a short couple of battles he comes out King of England, Duke of Normandy, Count of Flanders.
Louis VII of France still needs to ally with the other, elder, Blois lines and so still marries off his daughters to Champagne and Blois.
Meanwhile Eleanor of Aquitaine finds herself a nonAnjou to be her Duke.
TTL Philippe dies leading to his nephew Henry of Champagne being crowned King (there's no need for pseudoSalic Law here).
Eustace's line dies out, leaving the Champagnes as senior heirs to England-Normandy-Flanders.
During the wars to secure the north, Aquitaine and Toulouse end up in Aragonese orbit and later is removed from French suzerainty.