Found in The Marrows.

• Malignant Pincer (0-10m)
  
• Cerebral Crab (0-25m)

Found at Gale Cliffs.

• Cortex Decorator (0-5m)
  
• Splintered Crab (0-25m)

Found at Twisted Strand.

• Mire Screecher (5-25m)
  
• Effigy Crab (0-10m)

Found at Stellar Basin.

• Entangled Crab (0-5m)
  
• Imperious Lobster (5-50m)

Found at Devil's Spine.

• Sable Reacher (0-25m)
  
• Umbral Puppet (0m+)

The crab pot with the highest aberration chance (+10%) can be gotten fairly early in the game at
Gale Cliffs by placing one decorator crab and two rock crabs in the shrine at P3.

Otherwise, it's worth researching any of the first tier of crab pots - the basic crab pot has no aberration bonus. The first tier has +2%, second tier +4%, and the final tier +8%.

If you want to know the location of all the flags, check out this guide.