I personally use a combination of no-collision Tiled Background objects and a Sprite object with animation speed set to 0.

For the Sprite object, you only need one and can load up all your tiles as frames in the default animation. With the animation speed set to 0, you can set the start frame on each instance of the object to whichever frame you want, and then construct them as such.

I like to use a separate Tiled Background object for collisions in order to have more control over my level creation. I set the Tiled Background to be invisible and then have the box collision mode on, since it's cheaper on memory to do so (or at least it seems that way).

Don't take a shortcut and try to use large image files as levels, though. It's also generally good practice to have your images in powers of 2. You'll be able to save a lot of memory that way.

That's just my personal method on level creation. I'm sure you'll find vets here with far better methods, depending upon game types and all other kinds of variables and such.

Thanks so much! This whole answer was really useful!

I just wanted to ask, what's your favourite method for creating levels? Do you create tiles, and then place them inside of construct, or do you draw out the level in a drawing application, import it into construct, and then make invisible sold walls for collisions? Or do you do it another way? I am quite new to all this, and I wanted to be set in the right direction to start off with

Thanks in advance!