Video guide here: https://youtu.be/uTFdl5s6Vb0
If you don't have Forge already installed, here's a guide to get it installed: https://www.youtube.com/watch?v=mHvnHA04sbc
----> Step 1 Download Latest version of Flux NF4 12gb (recommended): https://huggingface.co/lllyasviel/flux1-dev-bnb-nf4/tree/main
----> Step 2 Put inside /Forge/webui/models/Stable-diffusion/

----> Step 3 Run Update.bat

----> Step 4 Start your Forge - Select FLUX and FLUX model.
Generate!

NF4 is significantly faster than other versions of Flux, like the FP8. I recommend using the NF4 model for faster speeds and lower VRAM requirements. It will run on 6gb+ vram machines.
The "regular" Flux models will give you somewhat better quality (at least for FP16) at a substantially longer generation time.
Optional model download: Flux FP8 17gb: https://huggingface.co/lllyasviel/flux1_dev/blob/main/flux1-dev-fp8.safetensors
For more information on optimizing settings (for low end systems mainly), check this post: https://github.com/lllyasviel/stable-diffusion-webui-forge/discussions/981
From lllyasviel github:
"If your device supports CUDA newer than 11.7 then you can use NF4. (Most RTX 3XXX/4XXX GPUs supports this.) Congratulations. Enjoy the speed. In this case, you only need to download the flux1-dev-bnb-nf4.safetensors.
If your device is GPU with GTX 10XX/20XX then your device may not support NF4, please download the flux1-dev-fp8.safetensors."
2.0 MP (Flux maximum)
1:1 exact 1448 x 1448, rounded 1408 x 1408
3:2 exact 1773 x 1182, rounded 1728 x 1152
4:3 exact 1672 x 1254, rounded 1664 x 1216
16:9 exact 1936 x 1089, rounded 1920 x 1088
21:9 exact 2212 x 948, rounded 2176 x 960
1.0 MP
1:1 exact 1024 x 1024
3:2 exact 1254 x 836, rounded 1216 x 832
4:3 exact 1182 x 887, rounded 1152 x 896
16:9 exact 1365 x 768, rounded 1344 x 768
21:9 exact 1564 x 670, rounded 1536 x 640