The phrase "add a side" is correct and usable in written English.
It can be used when referring to including an additional item, typically in the context of food or a meal order.
Example: "I would like to order the steak, and please add a side of mashed potatoes."
Alternatives: "include a side" or "add a side dish".
Add a side of science to your Turkey Day feast with these sticky, spicy and somewhat silly tidbits.
Add a side of tempura, pickled vegetables and a carafe of sake to round out the meal.
La Cantina's singing staff add a side of razzle-dazzle to your buzz, belting out Broadway standards, one-hit wonders and more daily at 6.30pm.
Simply add a side entrance and an extra few kilometres of tunnel, scientists told the Italian government, and you will create a unique facility.
Nektar's approach is to add a side chain to a derivative of morphine, which changes the way the molecule behaves in the body.
Order the phenomenal mussels, crowded into a bowl with monoliths of toast and a broth flaring with Aleppo pepper, add a side of archetypal frites, and you could easily think you are at the best French restaurant in town.
The accumulation of p-xylene in the column is avoided by adding a side product stream.
I added a side of sweet corn pudding, pepped up with a welcome jolt of chili oil.
Most trade agreements are ratified only after some last-minute issues are resolved by reopening talks or adding a side letter that carries equal force, the executive added.
He says he's proud of his southern roots because it's added a side to his character he might otherwise not possess.
So promising was mall development in Russia that Ikea, a privately held company run by the Kamprad family in Sweden, has added a side business in mall development through its Mega franchise, using Ikea as an anchor tenant.
