Get a large fabric Xilinx FPGA from ebay, reball it and make a simple PCB with Altium auto routing with JTAG, SPI flash, some memory. And find a license for Vivado.
https://commons.wikimedia.org/wiki/File:SanDisk_Fusion_ioMem...
It's basically useless for SoC development, though, as there's no memory on board, no I/Os other than PCIe, and no practical way to add any.