Meter and time signatures themselves are abstract concepts: the division of time into a regular pattern of accents.
How exactly those metrical accents are perceptible in actual music is achieved in different ways: dynamics (loud/soft), changes in pitch, rhythmic duration, etc. Basically you need some element to change. You need a minimum of two differing things.
The critical thing is music will be in a meter (or not) by virtual of what the music actually does. A common misconception is that simply writing a time signature means the music is actually in that time. But, it works the other way around. If the music is truly in a meter, then you apply that meter to describe the music.
In a way you are treating a drum backing track in a similar way. Or your expecting a meter will only be perceptible if something marks out time, like a metronome that dings on the first beat of a bar. But that isn't necessary. If the music is truly in the meter, you will be able to hear it without a time signature or a time keeping device.
Consider these unmetered, unbarred examples.
This makes duple, 4/4 time, because of the pattern of durations...
This makes triple, 3/4 time, using pitch change...
This is compound, 9/8 time, using dynamic accents...
Of course you would normally notate those examples with time signatures and bar lines for reading convenience.
Would playing a certain chord or note on every 1 beat work?
Yes, something like that will work.
A concept related to meter and bar lines is harmonic rhythm, the rate and pattern of chord changes. It's very common for music to change chord with each bar or simple subdivisions like one chord per two bars, or two chords per bar. If you described a harmonic rhythm pattern of chord changes every 4 beats followed by every 2 beats, you also have the information to know the meter is duple, either 2/4 or 4/4.
A simple two chord vamp would be enough to do what you're suggesting.
Arpeggiating a chord with a bass, hit the root only on beat one, that would make the meter clear even playing steady quarter notes.