Speed Controller Terminal/Connector?
You should consult with sales to get the best hardware selection and advice for EMI protection , e.g. twisted pair wire, small loops, fasteners.   Wire type.  The EMI radiated from each wire will be horrendous, so having twisted pairs at right angles reduces coupling.  CM chokes may be necessary as well heatsink and fan.

A good design will have no more than a 1% drop in voltage at operating current or 1% of the motor DCR winding resistance. (est. ~50 milliohm)

AWG 2 is 0.5127 mOhm/m.  Thus only 1/2 m for a wire pair yelds 1mOhm or 2% loss at startup which is great.

If you use 3m of cable, loss on AWG 2 cable alone is ;   

Pd= 3[m] * 2[wires] * 0.5127 [mOhm/m] *  300[A]^2 = 277 Watts  ( No Good)

Therefore if you need 3 m, use AWG 00 12mm dia. cable = 1mOhm (3m*2) = 2% of motor DCR.  Pd = 300^2*1 mOhm= 90 Watts for 30s max or 100A^2*1mOhm = 10W at rated 100A current.

Normally the wire resistance should be much less than the motor's and will rise in temperature with the resistance. 

If peak rating is 300A then start current could be as much as 10x the rated current of 100A or a start surge current of 1000A. With 48V this implies a 48mOhm winding resistance (DCR). 

Bolts that fit holes,  torqued to proper size crimped silver alloy spade lug with insulated cover such that it is “gas tight fitting”and withstands 50 lb pull test will work.  Any suitable rubber tape insulation will work.  Bolts should be high torque rated automotive type sized to proper length.   You must search for the best method for crimping or bolting the lug to wire with the same high torque. Resistance test  should result in no more than 6 uOhm resistance for 1W dissipation at 400A if you can measure uV to 1mV with some external current source.