Not sure why you specifically asked about Avalon, but there's a mostly open source one that's using Avalon Gen 2 chips:
http://drillbitsystem.com/2013/12/01/avalon-gen2-miners-by-drillbit-systems/( link to PCB/schematic/etc. at bottom )
There's also still the Nanofury designs, which takes Bitfury Gen 1 Rev1 OR Rev2 chip:
https://github.com/nanofury/NanoFury( There's 2-chip and 6-chip variants for which no schematic/PCB is available as of yet, but if you can find some pictures, it's easy enough to figure it out. )
And for the BE200 chip, there's the AsicMiner Tube designs:
https://bitcointalksearch.org/topic/block-erupter-tube-sales-information-thread-round4-price-at-1btc-per-ths-735728Note that all of these are already outdated in terms of chips. AsicMiner is working on their BE300, Avalon's on Gen 4, and Bitfury is working furiously (hah!) to get their next chip design finalized.
For anything else, you're mostly on your own, getting datasheets (NDA usually applies), messing with the hardware, trying to get it to work, all that.
As far as 'jell-looking stuff', if it was looking like a mostly clear fluid then that was probably flux. If it was more silvery and paste-like, it was solder paste. If it was something else, link to the video.
I agree with klondike that if you're not familiar with board assembly processes, you probably shouldn't be looking into this just yet.
