I have a piece of hornbeam wood which was cut green. I plan to make a couple of knife handles from it. Now it's extremely wet.
Does it make sense to try to force dry it? If yes then do smaller pieces dry with less cracking than larger ones? I'm not talking about drying speed right now. My assumption is yes because smaller piece has more freedom to shrink and move especially if it's cut from the periphery where the rings radius is larger (in extremity it will shrink linearly in one direction).
Does it make sense to try to force dry it?
Only you can answer this, since it's only your requirement that drives the decision to speed-dry versus just waiting for the wood to naturally season over a long time.
This piece, if dried whole, should be left for at least a year, unless you can put it somewhere unusually warm and consistently dry, ideally with good airflow too.
If yes then do smaller pieces dry with less cracking than larger ones?
If you don't seal the end grain, very much so.
If you do nothing to chunks of green wood cracks are virtually inevitable in most species, and they can be severe. However, given the exact requirement clarified in the Comments (small puukko style knives) it's possible that you could do nothing with a piece this size and still get numerous1 handle blanks from it.
I'm not talking about drying speed right now.
If you are intending to air-dry it's best practice to seal the end grain (see link below). This will maximise the yield2, giving you the most flexibility on what wood you can select from for each handle — choosing for grain, colour/figure — and so you have as much usable wood as possible for potential future uses.
If you split or saw the 'log' into wedges, these smaller pieces will air-dry substantially faster than the original piece of wood; note that it would be absolutely vital to seal the end grain if you do this because cracks in smaller pieces are more likely to intrude into wood you want to use. I've lost many handle blanks this way.
Additionally this would allow you to experiment if you'd like to, air-drying the majority of the pieces and trying out two of the fastest speed-drying methods — boiling and microwaving — which could potentially give useful handle blanks in half a day.
See A few notes on seasoning at the end of this Answer for some info on boiling handle blanks, and cautions about microwaving, as well as guidance on sealing the end grain with melted wax.
1 I'd say three for sure but as many as five might be possible.
2 If this chunk is long enough the yield could go up from 3-5 to as many as 10-12!
There are a number of species that are known as hornbeam, but since you're posting from Bulgaria, I will assume you have European Hornbeam (C. betulus). It's a very hard wood, and is prone to surface cracks when drying. With your small piece, and the intended use as knife scales, I would consider cutting the billet and drying the resulting small boards, rather than trying to dry the entire chunk. If you really only need to get a couple of knife handles, then to maximize the stability for drying, I would cut radial boards circa twice the thickness of the knife blanks you want, first by cutting a slice from directly through center that contains the entire pith, and then by cutting slices from the center of the remaining half circular chunks. You can continue to cut small slabs from the flats of the remaining quarters, if they are large enough.
Or, in to put it in shorter terms, quarter saw the piece.
You don't want to dry the resulting blanks too quickly, or they will likely surface check and case harden, particularly if you just air dry them. You may well get good results, though from drying them in a microwave. Just be sure to get good instructions on that technique. If you experiment with no guidance, you'll get it wrong. For wood of the thickness you'd be drying, you want to err well to the low end of the microwaving times in the instructions.
I dry a lot of wood like that (many different species) for bowl turning. and I find that splitting the 'log' in half (top to bottom, like firewood) does a great job of allowing to dry reasonably quickly and reduces the cracking. by splitting it in half you are dramatically increasing the surface area for the wood to dry from, and many cracks happen because the outside layers are drying faster than the inside putting a lot of stress on the wood, this also puts the 'crack' where you want it.
For what you want it for, I'd tend to split it into quarters, and I follow any major splits or cracks already in the piece.
