yes you can upload configuration file on switch flash using serial connection. Please check below link. is an upgrade guide for deploying a system software. it shows you how to upload system software to the flash, the process is the same for configuration file.
http://support.huawei.com/enterprise/docinforeader.action?contentId=DOC1000020013&idPath=7919710|9856733|7923144|16563
it is possible to connect a laptop to the switch? Ethernet cable, configure ip addresses, enable ftp, configure ftp user and then upload to file to the switch via ethernet?