There are two main reasons that your Irish soda bread might fall apart. The first is too much flour. I recommend using the “fluff and scoop” method: fluff up your flour with a spoon, then scoop the flour into your measuring cup lightly without packing it down. The second is too much kneading. Don’t knead this bread! It is only meant to be combined just so it stays together–no kneading whatsoever.