I recommend using the 28mm Olfa, straight handle rotary cutter for the Creative Curves Rulers (4", 3", 2" and 1 1/2" circular curves).
I recommend using the 18mm Olfa, straight handle rotary cutter for cutting the concave or inside curve of the Creative Curves Ellipse Rulers (2" X 4" and 1 1/2" X 3" oval curves). The 28 mm rotary cutter will also work but the 18mm makes it much easier to cut the inside oval curves.
These photos are intended to help by showing 'how to' position your arm and wrist when cutting the inside curves for either the circular or oval curves.
The first photo shows 'how to' position you arm with your elbow up, instead of your arm being horizontal to the table. This is the secret to easily cutting inside curves. Cut with your hand and arm almost perpendicular to the table (with just a slight angle back toward your body). This will place more direct force on the blade as it cuts through the fabric. In addition, less stress will be placed on wrists, arms and shoulders, thereby reducing the possibility of carpal tunnel problems.
Always cut the 'points' first.
The second photo shows the position for starting to cut the points. Look ahead of the blade while cutting (do not watch the blade) and turn your wrist while cutting (thinking - turn, turn, turn, etc.). Once the points have been cut, then cut the rest of the curve.
The reason it is important to cut the points first is that by cutting about 1" of fabric at the point, that will make sure that the seam allowance at the points will be accurate. Cut from the inside of the curve to the outside, away from the Ruler. Cutting toward the outside, away from the curve will ensure that the blade of the rotary cutter will not run into the Ruler.