Hi figaro, I can share how I approach such things. I usually use a Copic to lay a basic structure( a sphere in this case for the head of the flower and then I add the elements like leaves and petals. This very basic layin acts as a guide for me as I usually use a fine liner to ink it. I usually focus on the bigger shapes ignoring all the details at this point. I try and draw the shape of petals and other elements focusing almost entire on their contour. After than what I believe adds the most 3D look to it are contours. You can be done here if you are practising forms initially otherwise you can go ahead and add the shadows , just separating dark from light. I will try to upload an example whenever I can till then you can let me know if you found this useful. Feel free to ask me if you didn’t understand something.

Just uploading for today to make sure I'm keeping myself in check ;3 visualizing the plumb line is a but of effort but if I just enjoy myself things go much faster I feel.