How do you create regions without region3 ?

local region = Region.new(min , max)
--is there another way to do this

Hmmm...

This is my initial thought... This can be very unreliable tho, why not just use the real Region3? Don't be afraid, it's really not that complex.

A good tutorial: https://www.youtube.com/watch?v=XAwoodFJWos

Anyways...

local part = script.Parent --gets the part

local inRegion = {} --table of character/s inside the part

part.Touched:Connect(function(hit) --detects if a part is touched
	local character = hit.Parent --gets the character who touched
	local humanoid = character:FindFirstChild("Humanoid") --gets the humanoid of it
	
	if humanoid and not table.find(inRegion, character) then --checks if humanoid exists and if the character is not in the table yet
		table.insert(inRegion, character) --inserts the character to the table
	end
end)

part.TouchEnded:Connect(function(hit) --detects if a part is untouched
	local character = hit.Parent
	local humanoid = character:FindFirstChild("Humanoid")

	if humanoid and table.find(inRegion, character) then --checks if humanoid and the character is in the table
		for i = 1, #inRegion do --loops through the table
			if inRegion[i] == character then --checks if character
				table.remove(inRegion, i) --removes it
			end
		end
	end
end)