Here's a few tips for you

Usually I do a 20-30% water change every week in addition to refill the evaporated water. Do NOT do 100% water change, in ANYcase you should keep at least some of the old water.

You need a product that remove chlorine and chloramine form tap water and EasyBalance does NOT do that. you should get either Seachem's Prime or Tetra's Aquasafe.

No you don't have to empty and clean it every week, not even every month. Just kinda wipe off the build up while you're doing your water change.

You should get a siphon anyway, it make water change easier and you can suck up fish waste much easier. Plant do use fish waste as food, but over time it builds up and makes your tank bottom look dirty.

make sure the air stone doesn't create too strong of a current in your tank, bettas are rather poor swimmer dues to their long fins and tail.

Otherwise, you're good to go.

Ok, please put no fish in that size, as you suggest your self it can not be maintained easily.

Bettas do not live in small puddles in the wild (get any serious betta book on bio types and you will see this.)

Pennplax makes small filters that could work but bettas fins are one cell layer thin and any fast (bubbler or filter) movement will rip them (small tears invisible to the eye) and eventually the bacterial will do them in.

They also need a constant temperature of about 80 in the water and the air above - so lower water line and a heater that size is expensive (cheap ones can overheat). Plants (and they should have them, in the wild full of plants, adds security for them (they come alive esp in smaller tanks, adds dimension, adds micro cultures they pick on and helps with water chemistry.

The smaller the tank the more water changes. That is stress to any fish. Temp, ph, water quality even bacteria differences can cause stress.

The main reason for a larger aquarium (min would be 2.5) is for water quality maintenance.

If you insist on this small size (and again see ones in larger, how they swim all over, come alive are much happier) use one Anubias plant (won't need soil) low light can act as heater (or get very good heater) pennplax small filter (change once a week) and do partial water changes once a week at least (I did two when I did betta rescues). I used water (mine is aged and filtered in huge tub) with airline tube tied in loose knot to make it dribble in slowly.

As Kanvas mentions syphon from bottom and watch for curious betta to not get sucked up - don't look away for even a nano second!

Again, BEST to get a larger tank, you will find it much easier to care for and your fish will be SO much HAPPIER!

Betta breeders have to keep their huge amount of stock in cups bowls (and most change the water twice a day...

Poo/pee builds up toxins in minutes! It would be like us (got this on a fish forum) locked in a small bathroom, with no toilet, and someone shoves some food under the door (usually dried up cereal) one or twice a day. No room to exercise, and nothing to occupy our time (ie plants, rock scapes so on)... for some worse, direct bright light with no feeling of security (instinct says to hide) glare of light - IEEEE!

How about a feeder goldfish or a couple of guppies? Goldfish do not need heaters. Not sure about guppies.