Most EM programs require a SLOE; and SLOEs are completed by EM Residency Program Director/Clerkship Director of EM rotation, or EM Department Chairperson, or EM faculty, whichever official title is provided in your EM program. You can request a SLOE from each of your EM rotations.
In addition to other information, the SLOE provides an overall perspective on what a candidate offers to a training program, including non-cognitive characteristics such as professionalism, maturity, compassion, initiative, leadership and enthusiasm.
You should wait until 4th year rotations to get your SLOEs. This is because you will be compared to other 4th years. Most EM programs are looking for 2 EM SLOEs.