I pour baked baking soda inside the 2L bottle I plan to use, add the water (room temp), close the cap and shake for a minute or so. Done.

I don't know if it is only me, but I don't have a hard time with it. I also give the bottle a shake or two before every use.

Really? Dont you have a clumps forming at the bottom?

Over the course of using the batch, I get some precipitate at the bottom of the dosing vessel, is that what you mean by clumps? If I don't clean it out between uses the precipitate can build up to a pretty thick crust at the bottom, but it doesn't seem to mess with the amount I need to dose

No, I'm talking about mixing procedure. Once it dissolve I don't have precipitate at the bottom. When I pour the water or even little bit warm water into the baked baking soda then it became very hard and I have to crush it.

Really!?! I've never had that happen once!

Well, I never pour just a little bit of water in. I use tap water for my dosing chemicals because over the lifetime of a dosing mix, I figure the teeny amount of tap water going in to the system relative to the 50 gallon water changes I do with R/O water is probably negligible, so when I mix I always add water to the baking soda at the rate of a faucet open full blast, so maybe it just never has a chance to clump up. I also use the hottest water I can get out of my tap. A little stirring and by the time the bucket is full the water is completely clear, with nary of clump or floaty in sight.

When I make my next batch I'll try adding just a small amount of luke-warm water to the bucket first and see what happens.