In a piece of formative assessment, you mark the work and say how many mistakes and how many good points you observe, then ask students to revisit their work and edit/proofread/check it and see if they can spot the mistakes/good points.
You could get peers to mark and revisit work as well. Give students small exercises in the room to do this on – e.g. combine it with a writing exercise or a short performance. This will work with all assessment types from performance to written.
Give students a small exercise in the session. The exercise could just relate to one assessment learning outcome or many.
Mark the work (you may want to set another activity whilst you mark or you may use peer marking if appropriate).
Give the students their mark and the number of areas that were good or need work (but with no other feedback) and ask them to now mark it themselves looking for where the outcomes are achieved/not achieved.
Finally discuss with students how you awarded the mark and discuss common mistakes that were made and how to address them.
You could combine this with a writing exercise such as Harvard Referencing or the Cite Me TLA. You may want to have a discussion about marking rubrics.
With large groups, you can either run this as a solo activity and then put students into groups to discuss/adjust their decisions or you could have small-group discussions which contribute to a whole-group activity of generating one list.
Students will feel confident that they know what is expected of them in the assessment.
You may ask students to produce their own marking rubric for the assessment (See the Rubric Write & Reveal TLA)