I'd read that like 1-1. And yes, you need to read the word "centimeters" in the sentence. Otherwise, you would say to cut it into 4 to 5 pieces!! There's a big difference!
To read '4-5 cm', the correct way is option 1-1: "four to five centimeters." In this case, the numbers '4' and '5' represent a range, indicating that the rice cake should be cut into pieces that are between 4 and 5 centimeters long.