Bring a large pot of salted water to a boil and cook the linguine according to package directions; drain and keep warm.
In a large saucepan over medium heat, melt the butter.
Add the smashed garlic cloves and sauté in the butter until softened, about 1–2 minutes, then remove and discard the garlic with a slotted spoon.
Stir the chopped parsley into the butter.
Whisk in the all-purpose flour until combined and cook for about 30 seconds to 1 minute to remove the raw flour taste.
Slowly whisk in the half-and-half, then add the chopped clams and the juice of 2½ cans of clams; add a couple teaspoons of lemon juice and stir to combine.
Cook over medium heat, stirring frequently, until the sauce is hot and slightly thickened, about 3–5 minutes.
Toss the cooked linguine with the clam sauce and serve immediately, adjusting lemon juice to taste.
