I did that on a previous Canon MP. After a while, due to the "waste ink pad" being over full, a load of ink fell out of the bottom of the printer and ruined a desk top. If I were you, I would put the printer on a tray. The printer makers deliberately make it very difficult to change waste ink pads. Why they don't provide an accessible wast ink tank, I do not know.
I also retrieved the waste ink pipe from the back of the printer and extended it to a container, this works perfectly and no more messages re ink pads full! I can also see the waste ink being directed to the container which only needs emptying at very long intervals.