ERJ-170 First Officer reported he received SLAT FAIL EICAS on approach. Flight crew ran the procedure; declared an emergency; and landed normally.

Narrative

On final approach while configuring the aircraft for landing; we received a SLAT FAIL EICAS message when the slat/flap lever was moved from 2 to 3. We broke off the approach to run the QRH. The Captain took the aircraft and the radios and I began to run the checklist. The slats were indicating 3 in an inverse video amber setting and the flaps were indicating 3. The QRH prompted me to bring the slat/flap lever back to 2 and wait 10 seconds. After 10 seconds; the message did not go away and the slats remained in the same position; but the flaps did return to their previous position. I increased Vrf speed and noted the increased landing distance in accordance with the QRH. Since the flaps were still working; we selected flaps 5 to bring the Vref speed lower. The flaps moved to the desired location and the slats stayed in the same position. At this point we were getting low on fuel on due to un-forecast headwinds [en route] as well as two turns in a hold for [arrival] delays. Weather at the time was windy; but VFR. We did not have an alternate or any additional holding or contingency fuel on board.After the checklist was completed; I briefed the flight attendants and informed the passengers we had a slight malfunction that would require faster approach speeds and that they might see some airport personnel on the field to monitor the situation. Since fuel was an issue and we were so close to the field; I sent off a quick message to Dispatch informing them of the situation. The Captain did declare an emergency and as a precaution ARFF came out the runway to monitor our landing. The Captain did an excellent job monitoring the fuel situation as I was heads down for most of this time. We switched runways for additional distance. After reviewing the new landing data we did not feel that switching was necessary. Upon rollout; I noted the brake temperatures were in the green and ARFF confirmed that there was no smoke or fire from our brakes. We arrived at the gate without any further incident. The Captain had just come out of [recurrent training] where he received training on a partial or no flap landing and he said this helped him through the process. The crew used great CRM and worked well together which made the process run smoothly.