Prepare the shrimp: Peel and devein the shrimp. Save the heads and shells for the stock.
Soak the noodles: Soak the noodles in lukewarm water until softened but still firm. Drain and set aside.
Make the shrimp stock: Cook the shrimp heads and shells in oil until lightly browned. Add water, salt, pepper, and a bay leaf. Bring to a boil, then simmer for about 5 minutes.
Cook the shrimp: Add the shrimp to the boiling stock and cook until pink and opaque, about 1 minute. Strain the stock, then set the shrimp aside.
Boil the eggs: Boil the eggs for 10 minutes. Transfer to cold water, then peel and slice.
Brown the ground pork: Cook the ground pork in a wok or large pan until browned. Season with salt, then push to one side.
Sauté the aromatics: Add the garlic and onion, then cook until softened.
Brown the tinapa flakes: Add the tinapa flakes and cook until lightly browned.
Add the annatto and stock: Stir in the annatto powder, then add the shrimp stock. Season with fish sauce and black pepper. Bring to a boil, then taste and adjust.
Thicken the sauce: Stir in the cornstarch slurry. Simmer until thickened.
Cook the noodles: Cook the soaked noodles in boiling water until tender but not too soft.
Assemble the palabok: Drain the noodles, then arrange on a platter or divide into servings. Spoon the sauce over the top, then add the toppings. Serve with calamansi or lemon on the side.