First, make the pieces the same size
To add fractions with different denominators, rewrite them as equivalent fractions with a common denominator. Then add the numerators and keep that shared denominator.
The fractions must refer to the same-sized whole. A half of one small flatbread and a quarter of a much larger one would not measure the same portions.
OpenStax explains why the units need to match. Review equivalent fractions if that first step is new.
Half a flatbread plus a quarter
Take 1/2 + 1/4 of the same-sized flatbread. A half is two quarters: 1/2 = 2/4. Rewriting the half changes the pieces we count, rather than the amount.
Now add 2/4 + 1/4 = 3/4. The denominator stays four because the pieces are still quarters. Adding both top and bottom numbers to get 2/6 would change their size.
When neither denominator fits the other
For 1/3 + 1/4, twelve is a common multiple of three and four. Multiply the top and bottom of 1/3 by four to get 4/12. Multiply both parts of 1/4 by three to get 3/12.
Then 4/12 + 3/12 = 7/12. A larger common denominator can also work, but the least common denominator keeps the numbers smaller.
Does the total make sense?
Adding a positive quarter to a half must give more than a half. That quick check rules out 2/6, which is only one third.
Keep the method in order: same-sized whole, equivalent pieces, add, then simplify if possible. The actual addition is the familiar same-denominator step.