Here's an easy way to turn a few minutes into a quick practice session for both decoding and opposites. Sit pairs of students back-to-back on the floor and give each of them a copy of this card. Students will each choose or be assigned a column, left or right, and take turns as they quickly read down the list of antonyms.
You can easily differentiate this activity by highlighting one of the columns to help a student focus visually. You might also try assigning the right column to a student who would benefit from the scaffolding of using the opposite as a meaning clue for reading the word - it's always a bit easier to read the word "down" when you've just heard "up"!