Here I do program FPGA with a serial port RAM filler (homemade), and then I do upload ROMs (sooo long, you can show several blue progress bars), and then I do program FPGA first schematic : Z80+RAM+ROM, executing it, and then I do program second schematic : VGA is plugged on FPGA platform and does display "Ready".
Just about the "RAM filler", filling a RAM with data is perhaps the more important thing * about using FPGA platforms, do just remember that a RAM does keep its content as long as voltage is entered on it. So you can program FPGA without erasing RAM content. So you can program three FPGA programs : one for filling RAM, one for running a program using RAM, one for dumping RAM. Here I did use a serial transmit, but in fact, in last versions of FPGAmstrad, I do use a SDCARD with a homemade bootloader (filling RAM from SDCARD content)
I did use also Mock components, in first version of FPGAmstrad, FPGA platforms was too small, so I could have FPGAmstrad only with cool sound and low graphics, or else FPGAmstrad with cool graphics and no sound. Both using 100% of this old FPGA platform. A Mock component is a fake component, an empty one, just telling back "I'm OK, please thrust me I do exist" to others components trying to communicate with me (it's a entity with same in out ports as original but using constant output values)
*for programming a FPGA, the compiled binary is around 180KB, so do not expect about creating a RAM in FPGA itself. FPGA does contains also internal RAM (seduce ones, that can using two clock entries : one clock for data in an another for data out <3), but it is about 32KB. So an external 600KB RAM is best friend of FPGA.
=== Bootloader ===