The phrase "although it was easy" is correct and usable in written English.
You can use it to introduce a contrast or exception in a statement, often to highlight that despite the ease of a task, there may be other factors to consider.
Example: "Although it was easy to complete the assignment, I still felt a sense of accomplishment."
Alternatives: "even though it was simple" or "despite its simplicity".
An overhead mirror reflected the chef's moves, although it was easy to see without it.
Although it was easy to make an inexpensive and reliable red laser -- those $10 pen pointers have one -- scientists needed lasers that produced green and blue light as well.
Although it was easy to wonder what sort of tales Ms. Fenley was trying to tell, the contrasts between sharp and soft movements prevented "Short Stories" from drifting into amorphousness.
Although it was easy to paint Gourmet as the food magazine for the elite, it was a chronicler of a nation's food history, from its early fascination with the French culinary canon to its discovery of Mediterranean and Asian flavors to its recent focus on the source of food and the politics surrounding it.
Although it was easy to laugh at the pitiful performance of the Indiana Legion, which Morgan's cavalry so easily swept aside at Corydon and en route to the Ohio border, the militiamen did gain credit from some historians for delaying the Confederates, and thus aiding their pursuit by regular Union troops.
Cramer--like many others--felt that although it was "easy to identify the questions", she had been "reassured but not informed" at the conclusion of the meeting.
From comparison with exact results for a sphere and geometrical acoustics for a general obstacle, the formula appears to be effective in the middle range of frequencies, although it is easy to apply and its structure is simple.
Although it's easy to mistake them for punk desperados, their drive was actually weapons-grade self-deception.
Although it's easy to induce the effect, the biological purpose of blushing remains a matter of debate.
B ut although it is easy to dismiss a professor or make him sign an affidavit, it is not so easy to dismiss the issue of academic freedom.
