You can chant Namu Myoho Renge Kyo without a Gohonzon in front of you. Yes, you can.
Your heart carries the weight here. A dedicated corner of a room, kept clean and quiet, can hold your practice until a Gohonzon arrives.
The daimoku itself, Namu Myoho Renge Kyo, holds the entirety of the Lotus Sutra inside its sound. When you chant it, the Law vibrates through your life and through the space around you. This is true with a Gohonzon present. This is true while you build toward one.
Think of it this way. A mirror shows a face clearly, but a face is still a face in the dark, before any mirror is held up to it. The Gohonzon works like a mirror, showing you your own life reflected in the Law. Faith is the cause. Chanting is the expression. The mirror helps you see it. Your chanting still moves the Law through your life whether the mirror stands in front of you yet or not.
Keep your voice steady and clear when you chant. Sit upright. Speak each syllable of Na-mu Myo-ho Ren-ge Kyo distinctly. Give the practice a fixed time and place, five minutes or fifteen, whatever your day allows. This builds the ground your Gohonzon will stand on when it comes to you.
心を込めて、南無を捧げます
Namu Myoho Renge Kyo