Do you have a helper? I couldn’t do either of mine by myself, but with another person it’s not bad at all.
I find that different techniques work for different bunnies. My boy is relatively ok being picked up, so one person holds him, back against the holder’s chest and feet sticking straight out, one hand on his chest and one hand under his bum.
My other rabbit hates to be held, so I put her on a counter top with a towel. One person holds her down by wrapping her lightly in the towel and applying a little pressure to her shoulders, while the other person pulls her feet out once at a time.
Neither of mine would ever let me do it while they were on their backs, so just try new methods until you find the easiest one for your rabbit. Going to the vet and having them show you how to do it is also really helpful. I had mine done by the vet for a year or two before I could easily do it myself.