When you use the
align environment (Insert --> Math --> AMS Align), the columns are aligned as
rlrlrl..., as the usual use case is alignment around a relation. If you leave the odd columns (first, third, etc.) empty and place the content in the even columns, you will have just left alignment. This will, however, distribute the columns evenly over the text width, so if you have few/narrow columns, there may be a lot of white space between them.
An alternative then is to first add a normal display math environment (Ctrl + Shift + M) and within this add an
aligned environment: Insert --> Math --> Aligned. This has the same alignment as
align, so you would have to leave columns empty, but there won't be the extra space between them.