It's more like what we call DCAing (dollar cost averaging) which means buying regularly a portion of Bitcoin which is largely supported by many members of this forum there are other method one can consider when invest in Bitcoin which are listed by JayJuanGee in his thread
Once BTC accumulation targets are either established or at least there is some directional appreciation that you have to accumulate some bitcoin, then the next strategy would be to consider how to go about BTC accumulation. Surely, the best three ways to consider BTC accumulation is through 1) dollar cost averaging (DCA), 2) lump sum investing and 3) buying on dips. The consideration of these three strategies is also best in the order that I presented them. DCA has the advantage of having a kind of regular flow into your BTC investment that can really add up over time. Lump sum investing is many times not available for the vast majority of normies, and sure of course, if you have some abilities to lump sum invest there is nothing wrong with exercising such option because having a lump sum gives you options to invest it all at once or to even engage in some kind of DCA approach with investing the lump sum over time rather than all at once. Buying on dips is not a bad idea, but it requires timing the market
But your method though still supports buying in a whole because saving in a box before buying will still end up trying to buy in a whole which is not what anyone should be advised it better to buy regular because time matters if you don't buy at a point which you have the money something more important than saving might rag off your savings like health issues that is why we more support DCAing.