Open vent in floor

You did not say what if any other heating system is installed in your house, so I am going to assume that you have a forced air furnace and duct system in your house.

Here is what I did in a house I lived in and heated with a wood stove about 45 years ago. I had a duct company build me a large funnel duct piece to fit on top of the stove. The top of the funnel piece transitioned to a 7" round duct. I took the 7" round piece and ran it into the cold air return of the furnace. Then I manually turned on the furnace blower to circulate the air to the whole house. The stove heated the air that was collected and I was able to add heat the whole house. The furnace still heated as usual when the stove did not keep up with the needed heating.

If all you want to do is cut a hole in the floor to allow heat from the 1st floor to flow up to the next floor you could cut a hole in the floor and another hole in the ceiling below and add registers in both holes. I would buy large square floor registers say 10X10 or 12X12 to get adequate air flow. If you want you could have a duct company or an HVAC company make a square duct piece to fit into the square hole you cut to make sure that the air only goes to the room with the registers. If you go this route tell the duct fabricator what you want to do and he can make something that will work.

hope this helps