Skyscanner, check out airports that you would fly from. Find anywhere there are cheap flights for on the dates you want to travel and then find accommodation that matches the flights (Airbnb or booking.com).
We did this with 2 days to spare (so very few truly cheap flights around) and managed to sort a week in an apartment in Lanzarote for 3 of us for £1,100, of that the flights were £920. Pretty good for school hols and last minute flights!
Let me know if you want to know the name of the apartments – not the Ritz, but very clean, in a very good condition with a nice quiet pool area, just on the edge of town. The Canaries stay warmer when the rest of Europe is beginning to cool down and summer holiday resorts beginning to close down/turn in to the set of Coccoon.