This pair from http://www.knitaddicted.com/html/40.html - the BULKY YARN BOOTIE - was made with one strand Vannas Choice Autumn Print and one strand Vannas Choice Terracotta. It took a total of 6 ounces for the 68 stitch slipper. I used a size 8 needle since I tend to be a loose knitter and the pattern calls for a 9. I might consider opting for a 9 or even a 10 for a bit larger slipper but then would definately need more than 3 ounces of each yarn and since the Vannas prints are 3 ounces would probably choose a different yarn for a larger slipper.
I have made this pattern in the past and it is a fun easy knit in straight needles. You start by casting on for the bottom of the foot and after several rows of garter stitch you will change to stockinette and work short rows on the center stitches. The pattern calls for a 2" K1 P1 rib cuff but I chose to do 8 rows of garter stitch instead. I will definately be making several pairs of these.