As it turned out, just driving there and back (in the Routt National Forest service roads), was an extremely pleasant and pretty part of the day. I reached Big Creek Lake by heading north from Fort Collins, CO to Laramie, WY (awesome place : ), and then west on Hwy 230 to Cowdrey, CO.
At Cowdrey, instead of continuing south to Walden (even more awesome than Laramie and about another 10 miles from Cowdrey), I pointed my truck (here after referred to as "big blue"), west on, I believe, county road 6W. This actually stayed paved for around 5 miles or so before turning into a very (mostly) well maintained gravel road.
Here is a view of the Zirkel mountains. Big Creek Lake sits (roughly) at the northern end of the range (so, to the right of the photo).