So how does it feel like to pedal in smooth, fluid circle?

My pedaling on my hybrid feels quite rough and very uneven, especially evident when (attempting) one-leg drills on the trainer. I said "attempt" because doing one-legged drills is almost impossible. Try as I might, my leg momentarily "freezes" at between 10-1 o'clock. Then it drops down with a whoosh, then slows to a freeze again. It feel exactly like riding a roller coaster with a big drop: the train slows down near the summit, then picks up speed as it falls. I hate roller coasters and my legs feel the same way.

It's not much of a problem for me on flats but I feel this uneven pedal stroke is holding me back a lot on hills, or any incline for that matter.

I'm 156 cm (a little below 5'2) riding a hybrid with 170 mm cranks and clipless SPD pedals. I'm thinking the crank length may be part of the problem so I have ordered custom 153 mm cranks, but is there anything else I could do with my current cranks?

I'm very much a newbie rider with less than 500 km on my belt so I'm not expecting to be a smooth pedaler straight off the bat, but I didn't expect it to be such a struggle Any tips?